Recent Studies Of Avian Species Or Populations Biology Essay
Habitats undergo uninterrupted and world-wide increasing alterations due to turning urbanisation and agribusiness intensification Marzluff 2001 ; Shochat et al. 2006 ; Donald et al. 2006. These extended alterations of the landscape and back-to-back restructuring of home grounds can encroach on ecological procedures that influence the population growing potency of beings, peculiarly birds ( Lawton 1995 ) . For illustration, a assortment of surveies in Europe have shown that nest predation is reduced in human-settled environments compared to forest ( Snow 1958 ; Stjernberg 1979 ; Tomialojc 1980 ) while others have suggested that alterations in agriculture patterns could adversely impact endurance ( Robinson et al. 2004 ) .
In such a context of big scale environmental alterations, ecology purposes at understanding the grading of the responses of species and communities to temporal and spacial alterations in home ground construction and composing ( Bossenbroek et al. 2005 ) . In bend, such ecological informations can be used by policy markers and environmental directors to put marks, inform the pick of relevant baselines and to measure the degree of natural variableness ( Froyd & A ; Willis 2008 ) . Such direction patterns may turn to worsening populations confronting habitat impairment every bit good as invasive species colonising new home ground niches.
In measuring the importance of any home ground to genteelness birds, it is necessary to find non merely the figure of birds present but besides the part it makes to overall enlisting of new birds to the population, since territory denseness may non reflect habitat quality as defined by productiveness ( van Horne 1983, Vickery et Al. 1992 ) . Indeed, for nomadic species such a birds, presence is non plenty to bespeak sustainability, and seemingly feasible population of native birds into a given home ground may be in fact operation as population sinks, maintained through in-migration from spots of better quality home ground ( Pulliam 1988 ) .
Although one-year generative success ( immature produced per female per twelvemonth ) may be a more desirable metric for analyzing dad kineticss ( Thompson et al. 2001 ) , day-to-day nest endurance and back-to-back nest success ( the chance that a nest will fledge at least one immature over the nesting period. ) are thought to be an of import determiner of generative rates and, in bend, population kineticss. Consequently, a figure of surveies have highlighted the importance of spacial fluctuation in generative public presentation in keeping local bird populations from both theoretical ( Blondel 1985, Blondel et Al. 1990, Hatchwell et Al. 1996a ) and applied positions ( Galbraith 1988, Green 1988, Green et Al. 1997 ) . Nest success may be influenced by a broad array of factors such as nutrient resources ( Duguay et al 2000 ) , predator population size ( Smith & A ; Ostfeld 2003 ) , conspecific denseness ( Barber et al. 2001 ) , climatic events ( Baiser et al. 2008 ; Lehman et al. 2008 ) and may hence be a more sensitive index of the effects of home ground differences ( Armstrong et al. 2002 ) .
Recent surveies of avian species or populations ( Paradis et al. 2000, Driscoll et Al. 2005, Reidy et Al. 2009 ) back up the thought that multiple graduated tables affect nest endurance. These multiple graduated tables range from microhabitat ( nature of nest support, nest tallness and privacy ; Hatchwell et Al. 1996b, Weidinger 2002 ) to macrohabitat features ( comparative importance in habitat spot surface ( Moller 1988 ) , edge effects ( Chamberlain et al. 1995 ) . The two chief group of factors potentially impacting nest success, viz. resources and predation are besides considered utilizing variable spacial graduated tables: predation is in most instance considered at local graduated table since the impact on nest success will depend largely on local marauder densenesss ( Paradis et al. 2000, Stoate & A ; Szczur 2001, White et Al. 2008 ) , and nest conspicuousness ( Hatchwell et al. 1996b ; Weidinger 2002 ) . On another manus, resources are considered from local to larger graduated table, depending upon possible forage scope radius of birds during engendering season ( Fluetsch & A ; Sparling 1994 ; Boulton et al. 2008 ) .
There is hence a demand to measure how processes operate at different spacial graduated table ( Caldow & A ; Racey 2000 ) which is of involvement for widespread species and peculiarly those which have enlarged their genteelness scope following the colonisation of new home ground niches. For these species, the broad scope of environmental conditions they withstand is likely to impact more well their genteelness public presentation. However, so far, applied surveies have frequently concentrated on rare and/or worsening species, taking into history local context and it is ill-defined whether their determination apply to common and widespread species. Therefore, to day of the month, surveies comparing nesting success estimations across home ground gradients, landscape characteristics, and big geographic scope ( Paradis et al. 2000 ; Siriwardena et Al. 2000 ) remain comparatively scarce. An obvious restraint to that type of survey is that it requires a immense logistic support which is rarely available when utilizing voluntaries.
In this paper, we report a survey of temporal and large-scale spacial fluctuation in nesting success for the woodpigeon, Columba palumbus, throughout a 5 old ages supervising survey, from 2004 to 2008. Our analysis are based on extended national informations collected by professional technicians.
The woodpigeon is a common genteelness species in France, which inhabits all lowland home grounds ( Yeatman & A ; Jarry 1994 ) , with most birds happening on farming area, forest or homo associated home grounds from small town to big metropoliss. While its hereditary home ground was forest ( Cramp 1985 ) , it has taken chance from agribusiness development to colonise farming area ( Murton 1965 ) . Then, since the terminal of the XIX century, this species has been progressively present in urban home ground ( Cramp 1985 ; Tomialjoc 1976 ) . From a geographical position, the woodpigeon was present in all the northern half of the state ( Yeatman & A ; Jarry 1994 ) , but since the last decennaries, the engendering population has rapidly extended due south ( Yeatman & A ; Jarry 1994 ; Boutin 2001 ) . Simultaneously, the Gallic population has dramatically increased, and such addition is still traveling on to day of the month ( Birdlife International 2004 ; Roux et Al. 2009 ) .
Relationship between worlds and woodpigeons present contrasted facets: it is considered as a valuable game species by Gallic huntsmans and is now the first game species in France with respect to one-year bag size ( Lormee et al. 2000 ) . On another manus, this granivorous species is progressively considered as a plague by husbandmans, peculiarly in unfastened field country ( Murton et al. 1974 ; Inglis et Al. 1994 ) . In such a context, direction schemes are expected by both husbandmans and huntsmans with respects to engendering woodpigeon population, and nest success might be a cardinal constituent to take into history into such direction patterns.
We have identified 2 inquiries that need to be addressed in order to understand how woodpigeon genteelness success is shaped ; ( I ) what is its scope of variableness through clip and infinite, and ( two ) how of import are a set of environmental variables, including nesting and scrounging home ground construction, climatic events, nutrient resources handiness, predation force per unit area and denseness consequence, for such fluctuation in engendering success. We were peculiarly interested to compare nest success estimations between urban and non urban population, as we expect the late urbanization of woodpigeon to hold big impact on generative rates and farther Gallic engendering population moral force as a whole.
Material & A ; Methods
This survey rely on informations collected by professional technicians within a national monitoring programme developped by ONCFS since 2001. This monitoring was increasingly extended to all the national district from 2001 to 2008. At the clip we conducted our analyses, the two-third of the state were covered by this monitoring. To avoid geographical prejudice in our nest endurance appraisal, we used informations collected over the same part of the national district throughout the survey period ( fig.1 ) .
Nest seeking period occurred from March to late September, covering the full genteelness season of woodpigeon. Nests were located by walking indiscriminately or utilizing relevant information in the field such as locations of territorial vocalizing birds, flight shows, nest stuff conveyance. Perceivers were non constrained to prospect a fixed country over the survey period so the sites where nests were found could change every twelvemonth. However experient perceivers prospected most of the clip the same sites each twelvemonth. Each monitored nest was checked at intervals runing from 5 to 9 yearss ; on occasion, due to logistical restraints, intervals could be every bit long as 10 to 12 yearss. Merely nests visited at least twice were used into the analysis. Previous surveies of the effects of nest-visiting on open-nesting species were reviewed by Mayer-Gross et Al. ( 1997 ) , who concluded that any such effects are improbable to be of import. However, because monitoring of nest may increase the chance of predation and nest abandonment, perceivers took precautional steps to minimise their impact: they avoided consistently hassling grownups sitting on nest and, every bit frequently as possible, nests were checked at distance utilizing field glassess. Nests that were excessively high to see into were checked with a mirrored pole. All nests were relocated through elaborate field notes.
We used merely nests with confirmed activity ( eggs or baby birds ) in analyses. Woodpigeon incubation period last 17 yearss ( Cramp 1985 ) . Fledging period is variable and may run from 20 to 35 yearss ( Colquhoun 1951 ) . Throughout our monitoring, the youngest age at which biddies were known to hold successfully left the nest was 22 yearss and one time the biddies had left the nest, they could non be followed. The consequences of this work relate therefore to incubation and the first 22 yearss post-hatch. Chicks were aged utilizing a growing curve we have antecedently established, trusting upon flying length, length from the dorsum of the skull to the tip of the measure, and tarsus length. We were hence able to endorse calculate laying and hatching day of the months, and the stoping day of the month of the raising period when biddies reached 22 yearss old.
When possible we assigned a cause of failure ( i.e. , nest predation, inauspicious conditions conditions, abandonaˆ¦ ) to failed nests. We attributed nest failure to conditions or other natural events when nests were found destroyed and/or nests content were on the land below a atilt nest after a storm. Nest were considered to hold failed for unknown grounds when nest contents was empty with no ocular hints to bespeak the cause of failure. During incubation, we did non enter the nest destiny as abandoned until the eggs remained cold and unattended for at least 2 back-to-back visits. During the raising period, a nest was considered successful if it fledged i‚? 1 immature and we assumed that a nest had failed if immature disappeared & gt ; 3 yearss before the predicted fledging day of the month. Nests with unsure destiny were non included in analysis.
We standardized the beginning and the terminal of the genteelness season across the 5 old ages by utilizing the earliest day of the month a nest was located in any twelvemonth as the first twenty-four hours of the season ( incubation and rise uping periods: 6 March ) and the latest failure/hatching or fledging day of the month in any twelvemonth as the last twenty-four hours of the season ( incubation 23 October ; rise uping 14 November ) . If several genteelness efforts were made in the same nest throughout the genteelness season, we indiscriminately selected merely one per nest in order to obtain statistical independency of informations.
Candidate variables for researching fluctuation in nest endurance
We selected a set of variables ( listed in Table 1 ) that we considered to hold possible consequence on engendering public presentation in our species. These variables included: ( I ) nesting home ground ; ( two ) forage home ground ; ( three ) monthly precipitation sum ; ( three ) mean monthly minimum temperature ; ( four ) woodpigeon local copiousness ; ( V ) combined local copiousness of corvids, the avian chief nest marauders ( Jay: Garrulus glandarius, magpie Pica pica, and gloat Corvus Corone ) ; ( six ) nest location with longitude and latitude ; ( seven ) lift.
Justification and description and of the pick of variables
Nesting habitat – The features of home ground used by birds for engendering may dramatically determine nest success and in bend population kineticss ( O’Connor & A ; Fuller 1985 ; Martin 1992 ; Martin & A ; Clobert 1996 ; Chalfoun & A ; Martin 2007 ) . The impact of home ground on nesting success may move at different spatial-scale: nest success is affected chiefly by nest predation ( Chalfoun & A ; Martin 2007 ) and in such a context the geo-physical and vegetal features of proximal home ground ( referred to as nesting home ground ) are of peculiar involvement. Nesting home ground referred here as the homogeneous landscape unit within which the bird strains. Information on nesting home ground was collected by perceivers in the field at the terminal of nesting effort. We used a well simplified version of a cryptography system implemented by BTO for the Nest Record Scheme in United Kingdom ( Crick 1992 ) and designed to carry through the undermentioned demands: ( I ) to necessitate no adept botanical cognition, ( two ) to be based on the structural facets of bird home grounds but including simple floristic classs within the broads habitat types. The cryptography system consists of a simple four-level hierarchy. In the top degree are 4 major types of home ground and within each of the major home grounds are three farther degrees that are used to enter progressively elaborate information. In this survey, we merely used the first degree of categorization ; nest home ground was hence classified as: Woodland ( dominated by trees by and large greater than 5 m tall ) ; Farmland ( defined by all types of Fieldss, cultivated or grazed, etcaˆ¦ ) ; Urban ( dumbly built-up country, town Centres, and suburban country ) ; Villages ( little urban country with by and large less than 3000 dwellers, as scattered houses or other edifices ) .
Scrounging habitat – Complementarily, nutrient handiness may impact the ability of parents to optimise parental attention such as parental attending at nest, feeding frequence of the baby birds and hence their growing velocity, and in turn day-to-day nest success. In this instance, the relevant spacial graduated table to take into history in the description of home ground must incorporate the possible forage scope of engendering grownups. We hence described possible forage home ground used by woodpigeons during engendering utilizing digital land-cover informations collected in the CORINE Land Cover database ( CLC ) . CLC includes the chief home grounds for the whole state in immediate polygons classified into 44 different land-cover classs ( Bossard et al. 2000 ) . Among all the landscape variables available, we considered 4 groups of variables that we considered relevant to prove anticipations on woodpigeon nest success ; within agricultural home grounds, we identified a group representative of intensive agricultural lands, including all categories defined as “ cultivable lands ” , and a group representative of Mosaic agricultural landscape, including grazing land and all home grounds defined as “ heterogenous agricultural countries ” . Sing that both these home grounds groups were associated with high nutrient handiness through turning and mature cereals harvests, we predicted that an addition in the surface of both these home grounds into the woodpigeon scrounging radius should be associated with a better nesting success. We besides identified a “ forest ” home ground group, including broad-lived, cone-bearing and assorted woods and chaparral and/or herbaceous floras associations. We predicted that forested home grounds were associated with a high predation force per unit area and low nutrient handiness, and therefore a decreased nesting success. Finally we identified an “ urban ” home ground group, including all unreal surfaces. Urban country do non offer important nutrient resources to woodpigeon, nevertheless such country are considered to be associated with low densenesss of marauders potentially feeding upon woodpigeon nests, we predicted hence an addition in nest success along with increasing urbanised surface within the foraging radius.
Until 2008, perceivers did non roll up geographical co-ordinates of every nests, we hence assigned to the nest the co-ordinates of the commune within which it was found. To look into the consequence of scrounging home ground on nest success, we so extracted habitat composing informations within a 5 kilometer radius centred around those co-ordinates. We assumed that a 5 kilometer radius allowed us to correctly describe scrounging habitat composing in the locality of the nest, and that it was biologically meaningful with respects to scientific informations available on woodpigeon forage scope ( Haynes et al. 2003 ; Lormee et Al. 2002 and unpublished informations from a radio-tracking survey ) . In order to look into that scrounging home ground was right defined following such a design, we investigated specifically in 2008 the correlativity between scrounging habitat composing within a 5 kilometer radius utilizing either the commune coordinates or the really coordinates of the nest. The relationship was extremely important ( N = 1899 nests ; Farmland: RA?= 0.93, T = 158.52, P & lt ; 0.0001, incline = 0.934 ; Forest: RA?= 0.86, T = 106.68, P & lt ; 0.0001, incline = 0.932 ; Urban: RA?= 0.87, T = 112.96, P & lt ; 0.0001, incline = 0.974 ) .
Monthly Precipitation & A ; temperature – Woodpigeons use unfastened and level nests frequently built rather rudimentarily with branchlets. Consequently, nests are peculiarly vulnerable to meteoric event such as heavy rain, air current and cold temperature. We hence predicted a negative impact on nest success from increasing sum of precipitation and diminishing minimum temperature.
Precipitation and temperature values were obtained from MeteoFrance climatic database, trusting upon a model of ca 700 meteoric Stationss covering all the state and roll uping informations daily. To capture spacial and temporal difference in precipitation sum or minimum temperature, we calculated each nest value by pull outing the monthly precipitation and temperature values measured over the active nesting period. For every nest, we assigned meteoric informations from the nearest step station ( average distance, Incubation: 13.6 A± 0.2 kilometer ( SE ) , n = 982 ; Rearing: 13.8 A± 0.2 kilometer, n = 1024 ) . When the active nesting period was wholly encompassed within the same month, we straight used the monthly sum of precipitation or the average monthly minimum temperature. If the active nesting period overlapped two back-to-back months, we so calculated an averaged value over the two months period.
Abundance of woodpigeon and corvids during engendering season: we predicted ( I ) a positive relationship between nesting survival rate and woodpigeon copiousness since sites demoing a better success should be more attractive for engendering birds and ( two ) a negative relationship between nesting success and corvids copiousness as an increasing copiousness in corvids should take to a addition in predation force per unit area. Information on woodpigeon and corvids copiousness during engendering were taken from a national point count grid ( ACT supervising plan ; see Boutin et Al. 2001, 2003 for full description of the methodological analysis ) where territorial vocalizing birds are counted each twelvemonth through two 10 proceedingss Sessionss long ( preciser pour corvids que ce sont surtout ceux qui sont vus? ) , between early April and mid June. Woodpigeons were surveyed since 1996 but corvids merely since 2008. Based on these point count informations, a “ local ” woodpigeon copiousness was assigned to each nest monitored into our survey utilizing the figure of birds recorded in the closest point count and during the same twelvemonth the nest was monitored ( average distance, Incubation: 9.4 A± 0.1 kilometer ( SE ) , n = 982 ; Rearing: 9.5 A± 0.1 kilometer, n = 1024 ) . For corvids copiousness, we assigned to all nesting attempts the copiousness estimated in 2008, sing that it was more or less representative of corvids copiousness throughout the survey period.
Elevation and location of the nest – As we limited the figure of environmental covariates used in this analysis, we could non except that other covariates might hold a important consequence on spacial fluctuation in nest endurance. Thus we besides included some geographical covariates such as latitude, longitude, and lift of the commune within which the nest was found.
Following the recommendation of White and Burnham ( 1999 ) , we centred all single covariates around the norm and standardized them by the standard divergence in the clip series covering the survey period.
To minimise auto-correlated experimental covariates we created a correlativity matrix, observing those extremely correlated ( r i‚? 0.7 ; REF? ) and in response retaining merely that with the lowest Phosphorus values in an univariate theoretical account.
We used Mayfield estimations of day-to-day survival chance as a step of nest success, which is the estimated chance of a nest lasting a twenty-four hours within a defined phase of the nest rhythm ( see Mayfield 1975 for the rules of Mayfield method ) . Ratess of nest success were estimated utilizing the daily-survival calculator ( DSR ) available in plan Mark ( White & A ; Burnham 1999 ) . DSR was so used to gauge cumulative chances for nest endurance. Because day-to-day endurance can change across nesting phases, separate Mayfield estimations were calculated for each phase ( incubation, cuddling ) and multiplied together to deduce the overall estimation of nesting success.
Nesting effort expiration ( failure or Hatching/fledging of the immature ) was assumed to happen half manner between the next-to-last observation of active nest and first observation of failed or Hatched/fledged offsprings.
We used a modified signifier of Akaike ‘s information standard, AICc ( Burnham and Anderson 1998 ) for theoretical account choice. The theoretical accounts with the lowest AICc value was considered to hold the best tantrum ; theoretical accounts with AICc values differing by i‚? 2.00 units were considered every bit supported, in which instance the theoretical account with the fewest parametric quantities was chosen ( Lebreton et al. 1992 ) . We used the symbol “ iˆ« ” to mention to linear effects and the symbol “ i‚? ” to mention to interactions. We used “ . ” to denominate changeless theoretical accounts. Estimates were constrained utilizing a logit nexus map. We used the statistical bundle MARK 5.1 ( White and Burnham 1999 ) to obtain maximal likeliness estimations of nest endurance and fit statistics, under assorted theoretical accounts.
The theoretical account choice was conducted following a scheme described in Grobois and Tavecchia ( 2003 ) and Grosbois and Thompson ( 2005 ) . Prior to proving the covariates that might underlie any spacial fluctuation in nest endurance, we built and compared the decreased theoretical accounts nested in the going theoretical account. For both genteelness phase, the going theoretical account was S ( Year i‚? Month ) . This measure of the analysis permitted the definition of a “ mention theoretical account ” that captured the most of import fluctuation in nest endurance, without trusting on specific premises refering the covariates underlying their temporal fluctuation ( afterlife called “ Time theoretical account ) . We performed the choice of the mention theoretical account independently for incubation and raising.
Once the mention theoretical account had been defined, we tested the covariates potentially implicit in clip fluctuation ( listed in Table 1 ) . For each genteelness phase, we performed a measure up process in which, at each measure, we selected among the covariates considered as potentially underlying fluctuation in nest endurance the one whose add-on to the theoretical account led to the best united AICc and parsimony standard. The theoretical account including all the covariates selected for depicting fluctuation in nest endurance chances will be hereinafter referred to as the “ concluding theoretical account ” . We did non include multinomial or interaction footings in these theoretical accounts because this would hold given rise to increased jobs of theoretical account choice and reading. Environmental covariates were all standardized to let a direct comparing of their comparative importance. Means and estimations are presented i‚± SE.
Over the whole 2004-2008 period, we monitored a sum of 5505 nests during incubation and 5412 nests during nestling phase that were observed severally for 53285 and 81041 exposure yearss ( see Table 2 & A ; 3 for more inside informations ) .
Annual failure rate averaged 43.6 % i‚± 1.6 during incubation and 30.8 % i‚± 1 during nestling phase ( Table 3 ) . Depredation was ever the chief cause of engendering failure and accounted for an norm of 50 % i‚± 3.7 of failed nests during incubation and 44.3 % i‚± 2.7 during cuddling stagerearing.
Temporal fluctuation in nest endurance
In both genteelness phases, clip theoretical accounts performed better than changeless theoretical account. Choice from the going theoretical account suggested an linear consequence of twelvemonth and month on nest endurance during incubation, and an consequence from the interaction of twelvemonth and month during the nestling phase ( Table 5 & A ; 6 ) . Annual nest survival rate ranged from 34 i‚± 1 % to 46 i‚±1 % during incubation, and 58 i‚± 1 % to 63 i‚± 1 % during the nestling phase ( Fig. 2 ) . Nest endurance during incubation was ever below 50 % and hence lower than during the nestling phase but besides more variable between old ages. In both genteelness phases, nest endurance significantly increased throughout the genteelness season, being the lowest from March to may and climaxing during September-October ( Fig. 3? ) . Evaluation du succes mensuel sans effet habitat a sortir
Environmental covariates underlying fluctuation in nest endurance.
The concluding theoretical account depicting for fluctuation in nest endurance during incubation included effects of proximal home ground, minimum temperature, latitude, forest screen and corvids copiousness ( Table 5 ) . During the nestling phase, the concluding theoretical account retained effects from proximal home ground, corvids copiousness, longitude and latitude, and cultivable land screen ( Table 6 ) . In both genteelness phases, the add-on of other covariates to these theoretical accounts did non significantly better the tantrum of the concluding theoretical account ( i?„AICc & lt ; 2 ) .
For both engendering phases, the add-on of proximal home ground to the clip mention theoretical account improved the theoretical account well, with a lessening of severally 139.6 and 188.3 i?„AICc ( Table 5 & A ; 6 ) . Whatever the genteelness phase, nest endurance was the lowest in farming area and forest home grounds, and the highest in urbanised home grounds ( Fig. 4 ) . Among the latter 1s, nest endurance was systematically higher in small towns compared to towns ( Fig. 5a, B ) . The difference in nesting endurance between rural and urban home grounds reached at least 14 % ( Forest/urban ) during incubation and 15 % ( farmland/urban ) during the rampant period.
Models including consequence from precipitation, woodpigeon copiousness, mosaic and urban home ground screen, received no support. Other covariates included in the concluding theoretical account accounted merely for a comparatively significant portion in the residuary fluctuation of nest endurance. Table 7 shows the estimations of the incline for the covariates retained in the concluding theoretical accounts. During incubation, nest endurance was positively affected by minimum temperature, and, to a lesser extent, by corvids copiousness, but reciprocally related to the sum of forest land screen within the foraging radius. Among those covariates, the consequence of minimum temperature was stronger than the others. During the raising period, success was once more affected positively by corvids copiousness and the sum of cultivable land screen, with no pronounced difference in the strength of the relationship between these two covariates.
For both engendering phases, concluding theoretical accounts besides included some effects from latitude merely ( incubation ) or both latitude and longitude ( rise uping ) , giving no functional account by itself but proposing that a staying portion of fluctuation in nest success was explained by other spatially structured factors that we did non utilize in this survey. During the incubation period, the consequence of latitude was every bit strong as the effects from forest screen or corvids copiousness. During the nesting phase, longitude and latitude even ranked in 2nd place after corvids copiousness consequence.
The cognition of clip and spacial fluctuation in engendering public presentation along with the designation of environmental factors underlying such fluctuation is critical for doing anticipations with regard to the kineticss of populations. Among the assorted parametric quantities underlying genteelness public presentation, nest success has been suggested to be the most of import constituent ( Wiklund 1995 ) .
The step of temporal fluctuation of nest success is so necessary to measure the possible effects of its variableness on population tendency. Temporal comparing of nest success may be limited when trusting on distinguishable surveies which use uncomparable calculators. Our survey offers the advantage to utilize the same calculator and field methodological analysis over the five old ages survey period, doing easier such comparing. With respects to spacial fluctuation in nest success, the survey of species engendering over big country and utilizing a broad scope of engendering habitat types is debatable since the consequences of local-scale surveies might be representative merely of a specific home ground and will non consistently use to the whole population. Further, local-scale procedure might constrained by home ground features at the landscape graduated table ( Peak et al. 2004, Donovan et Al. 1997, Hartley and Hunter 1998, Tewksbury et Al. 1998 ) . To understand such big graduated table forms, it is hence necessary to measure how processes operate at different spacial graduated tables ( Caldow and Racey 2000, Ormerod and Watkinson 2000, Chalfoun and Martin 2007 ) and for all chief genteelness home grounds used by the targeted population. Consequently to logistical costs built-in to such design, few surveies investigated big spatial-scale fluctuation in nest success at intraspecies degrees ( Paradis et al. 2000 ; Donovan et Al. 1997, Beauchamp et Al. 1996, Siriwardena et Al. 2000 ) . This survey on woodpigeon nest success is in maintaining with such attack and offers the chance to widen it to a non-passerine and tree-nesting species.
Variation of nest endurance between engendering phase
During the survey period, hatching chance was lower than fledging chance. Such consequence was extremely consistent since it was observed for every twelvemonth and all genteelness home ground. Interspecies comparings are uneasy to execute since other surveies have been conducted most of the clip in a specific country and during a short clip period, and reference chiefly passerines species. Some surveies found a higher success during incubation ( Holcomb 1972, Siriwardena et Al. 2000, Lantz and Conway 2009 ) , other during nestling phase ( Young 1963, Robertson 1972, Schaub et Al. 1992, Hatchwell et Al. 1996, Paradis et Al. 2000, Burhans et al. 2002, Schmidt et Al. 2008 ) , or no important difference ( Donald et al. 2002 ) . Interestingly, Siriwardena et Al. 2000 analysed temporal fluctuation in nest endurance of farming area birds from 1962 to late 1970ss utilizing “ twelvemonth block informations ” and showed that for some periods, the difference between engendering phases in nest success could change by reversal within the same species, which pinpoints the demand to work over long periods to correctly gauge the scope of fluctuation in nest success. More surprisingly, in both Colombides species that were analysed in this survey ( stock dove Streptopelia decaocto and turtle dove S. turtur ) , success during incubation was higher that during nestling phase. That could ensue from a different context in predation force per unit area since marauder populations in United Kingdom were low and retrieving during the period of the survey ( 1960ss to early 1890ss ; Marchant et Al. 1990 ) .
Temporal fluctuation in nest endurance
Annual fluctuation in woodpigeon nest endurance was much more marked during incubation than during the nestling period: the maximum one-year difference in hatching chance reached 35 % whereas it reached 9 % for nestling phase. In 3 old ages out of 5, nest endurance rates ranked likewise in both genteelness phases ( 2004, 2005, 2006 ) ; 2004 and 2005 had severally the highest and lowest values in both phases. If sing changeless all other constituents underlying engendering public presentation, so most of the one-year fluctuation in this parametric quantity might be driven by nest endurance rate during incubation. Whatever the genteelness phase, the subsequently the nesting effort was initiated in the genteelness season, the higher was nest endurance. Such consequence might look ambiguous since fluctuation in bird genteelness success is frequently shown to diminish in the late portion of the genteelness season ( ref XXX? ) . However, some other species show an addition in nest endurance as the genteelness season advancement, like the burrowing bird of Minerva, Athene cunicularia ( Lantz & A ; Conway 2009 ) or the Moutain plover, Charadrius montanus ( Dinsmore et al. 2002 ) . In our survey, such seasonal addition might ensue from a alteration in predation rate ( displacement in marauder community or in handiness of alternate quarries ) . Alternatively, nutrient handiness extremums in September-October, when harvested cereals field provide big sum of set aside seeds. In the instance of the woodpigeon, this higher nest endurance tardily in the season relies on a much lower figure of engendering effort, raising the possibility that this higher nest success is due to more experient birds with higher parental accomplishment. One can inquire why genteelness should halt in September if nest success is so high at that clip but it should be reminded that we measured nest endurance merely during incubation and nestling phase, non taking into history the post-fledging period, when immature birds have left the nest but are still fed by grownups. Young woodpigeon organic structure size is merely two-third of grownup organic structure size when they leave the nest ( Murton 1965, Robertson 1986 ) and choice force per unit areas might originate tardily in fall and winter, chiefly through fluctuation in nutrient handiness, to negatively affect endurance rates of late born woodpigeons ( RefXXX ) .
Consequence of environmental variables on nest endurance
In both incubation and nestling phases, concluding theoretical accounts included a few figure of environmental consequence, with limited support for our hypotheses refering scrounging habitat consequence on nest endurance. Perversely, the environmental variable accounting for most of the fluctuation in nest endurance was nesting home ground, proposing that local graduated table procedure such as habitat spot type consequence may be prevailing over procedures moving at landscape degrees such as scrounging home ground types. The most dramatic consequence was that nest endurance was much higher in urbanized home grounds than in wood and farming area. If taking into history nest endurance over the whole genteelness effort, by doing the merchandise of incubation and nestling endurance rates chances, so one clasp in rural or forested home grounds would hold merely 10 to 20 % of opportunity to bring forth at least one offspring while urban would make 25 to 45 % of opportunity, that is a two-threefold difference between rural and urban home grounds.
Greater nest endurance in urban than rural home grounds have been shown for other species holding late colonized urban home grounds on assorted continents ( Kentish et al. 1995, van Heezik et Al. 2008 ) . Tomialjoc ( 1980 ) had antecedently shown that woodpigeon productiveness in urban could be much higher in some Polish metropoliss compared to adjacent rural populations. Food handiness within urban country is improbable to explicate the higher nesting success of woodpigeon since most birds feed outside of the towns ( Tomialojc 1980 ) . This higher urban nest endurance has frequently been related to a lower predation force per unit area ensuing from lower marauder copiousness ( Snow 1958, Stjernberg 1979, Tomialojc 1980, Tomialojc et Al. 2004, Piotrowski and Wesolowski 1989, Newton 1193 ) and/or alteration in marauder community ( refXXX ) . However these consequences are ambiguous since some surveies have found increasing nest predation in more urbanized countries where there are more generalist marauders, both avian and mammalian ( Jokimaki & A ; Huhta 2000, Thorington and Bowman 2003 ) , whereas others reported diminishing nest predation and worsening marauder copiousness with increasing human lodging denseness ( Wilcove 1985, Donovan et Al. 1997, Gering and Blair 1999, Haskell et Al. 2001 ) . These differences between surveies might besides stem from the definition of urbanised home ground they use ( see Chamberlain et Al. 2009 ) since urban country may greatly change in habitat composing ( ratio between green infinite, residential lodging, industrial/commercial edifices ) . It should be noted that in our survey, nest endurance was higher in small towns than in larges metropoliss, peculiarly during the incubation phase. In our home ground coding categorization, “ small town ” encompassed scattered houses to little towns of less than 3000 dwellers. Several hypotheses might explicate the difference in nest endurance between small towns and towns, ( I ) woodpigeons engendering inside small town have less distance to go to nutrient resources, leting shorter absences from the nest, ( two ) home ground microstructure in small town may offer more chances to hide nests ( continuity of hedge and brushs in garden ) , or to settle them in topographic points less accessible to marauders such as beams under roof in opened shelter, ( three ) big metropoliss welcome more Parkss more or less forested which give chances to marauders to settle more durably and in larger Numberss, peculiarly for corvids but besides for mammalian marauders such as squirrels.
Nests found both in forested and farmland home grounds had the lowest endurance rates and during the incubation phase, and nests found in forested home ground had a lower endurance rate than in farming area. Surveies that investigated nest endurance rates in forested home grounds found low values ( Boulton et al. 2008 ) , in some instances similar to survival rates measured in next farming area home ground ( Hatchwell et al. 1996 ) . Forest country might be considered as a low biomass district for scrounging woodpigeons which may necessitate to go forth the nest unattended more often and hence more vulnerable to marauders ( Schmidt 1999, Zanette et Al. 2000 ) . It has besides been shown that within forested home ground, nest endurance decreased from nucleus country to the border, due to an increasing predation force per unit area on the border ( Benson et al. 2010, Driscoll et Al. 2005, Donovan et Al. 1997, Hatchwell et Al. 1996 ) , although some plants found grounds of an “ border consequence on ground-nesting clubs but non shrub or canopy-nesting clubs ( Lloyd et al. 2005 ; Chamberlain et Al. 1995 ) . In our survey, the “ Forest home ground ” class encompass brushs to big forest spot. Woodpigeons nests monitored in forested home grounds were preponderantly found in little spot of a few hectares, and most frequently detected within the border of the spot. It is hence sensible to believe that our appraisal of nest endurance in forested home ground might be a spot underestimated because nest monitoring occurred most frequently in edge country of wood spots, where nests face a higher predation hazard, peculiarly in disconnected landscapes ( Donovan et al. 1997, Andren 1995 ) , where nest marauders and peculiarly members of the Corvidae household addition in copiousness, activity and species profusion ( Chalfoun et al. 2002 ) . Underestimate of nest endurance could besides ensue from a prejudice in nest tallness distribution within our informations set. Perceivers found chiefly nests between 2 to 6 metres high, that is in a tallness scope where nests are exposed both to mammalian and avian marauders ( Martin 1995 ) . Nests higher in the canopy suffer predation largely by corvids ( Remes 2005 ) with, perchance, a back-to-back lower failure rate ( Murton 1958 ) .
Woodpigeons nesting in farming area home grounds use chiefly hedgerows and scattered trees. The low nest endurance rate we measured may be unexpected since engendering grownups are close to nutrient resources and should go to the nest more expeditiously. Again, the habitat categorization we use conceal a big diverseness in home ground construction, peculiarly with respects to the hedgerow denseness. It is likely that perceivers were likely to happen more easy severely hidden nests in comparatively debauched hedgerows complex than in preserved bocage. As nest failure rate additions along with atomization strength of hedgerows ( Hinsley and Bellamy 2000 ) , our estimation of nest failure might hold been somewhat overestimated. However, it should be noted that Gallic agricultural landscape is now preponderantly dominated by openfield system ( Agreste 2010 ) , with debauched hedgerows systems, so our consequences are likely to be representative of the whole farming area home ground.
Scrounging home ground
Nest endurance was negatively related to importance of forest land screen within the foraging radius during the incubation period, and positively linked to the sum of cultivable land screen during the raising phase. However, these effects were really weak within the concluding theoretical account. Such effects are consistent with the consequences we obtained with respects to the proximal home ground. During incubation, the addition of forest country may likely cut down the country where grownups can entree to nutrient resources and lead birds to scrounge longer/farther to happen nutrient, go forthing nest unattended. Why such relationship does non use for the nestling phase remains ill-defined. Pigeons and plunge eggs are pure white, and hence unattended nests with eggs may be more conspicuous and noticeable by marauders than nests with biddies.
The addition of nest endurance during the nestling phase along with the sum of cultivable land screen suggests that higher nutrient handiness may favor shorter scrounging trips for grownups, a higher eating frequence and accordingly improves chick growing rate. Chicks turning faster are able to pass less clip at nest and hence cut down their period of exposure to nest marauders.
An unexpected consequence of our survey was the positive relationship in both engendering phases between the 2008 corvids copiousness, used as a placeholder of predation force per unit area, and nest endurance rate. In Europe, corvids are considered to be the chief marauders of open-nesting birds ( Groom 1993, Del Hoyo et Al. 2003 ) and peculiarly Colombides species ( Murton 1965, Murton and Isaacson 1964 ) . Descriptive and experimental surveies have shown a negative impact of marauder copiousness on nest endurance ( White et al. 2008, Donald et al. 2002, Anthony et Al. 1991, Tapper et Al. 1996, Paradis et Al. 2000 ) . Our consequence may look to be in contradiction with the readings of our consequences on nesting and scrounging habitat consequence on nest endurance which frequently call on predation statement. However, paradoxes are non uncommon in a multivariate model and are best explained by looking the incline of each variable to measure comparative influence on nest endurance. The theoretical account including the consequence of clip and nesting home ground was ill improved by the add-on of environmental. In the incubation phase, the incline of the corvids copiousness consequence ( 0.044 ) was the weakest among all variables selected in the concluding theoretical account. Conversely it ranked foremost in the nestling phase ( 0.13 ) . This evident paradox might be better understood if sing the European context with regard to predation force per unit area: Martin and Clobert ( 1996 ) mentioned that nest predation rates are lower in Europe than in North America for open-nesting birds, and that “ large-scale alteration of the environment may hold reduced evolutionary restraints of nest predation on life-history traits in European systems. Consequently, forms of nest predation and the importance of nutrient versus nest predation to life-history fluctuation may hold changed such that nutrient may be a more of import influence in European systems ” . Consequently, our survey suggests that predation force per unit area might non be a powerful confining factor on woodpigeon nest endurance, which might be more under the influence of home grounds construction and back-to-back entree to nutrient. The positive relationship we obtained might exemplify that home ground in which woodpigeon nest endurance is high are likely besides those that are favoured by corvids to engender. Indeed, it should be noted here that the consequence of marauders on nest endurance may be ambiguous and may non use likewise to all unfastened nesting bird species. Average song thrush nest endurance have non declined in parts of Britain with increasing magpies densenesss ( Gooch et al. 1991 ) . In some experimental surveies which showed a decrease of nest failure following the control of marauders populations, the writers recognized that such consequence might be confounded by concurrent and attendant debut of habitat direction steps ( White et al. 2008, see besides Stoate and Szczur 2001 ) . Andren ( 1995 ) mentioned that displacements in marauder individuality between fragmented and unfragmented landscapes may do nonlinear relationship between predation rates and landscape construction. Additionally, many surveies focused on land nesting bird species ( Donald et al. 2002, Anthony et Al. 1991, Tapper et Al. 1996 ) , and a bulk reference passeriform birds species, therefore the inquiry remains of their application to non passerine species.
We acknowledge that some cautiousness must be taken in the reading of the consequences about predation impact with respects to our ain bounds in the manner we approximated predation force per unit area. The chief bound root from the fact that our appraisal of corvids copiousness index relies on one twelvemonth merely ( 2008 ) , therefore the beginning of fluctuation in marauder copiousness was merely spacial and non temporal. Furthermore, the chief distance between woodpigeon nests in our informations set and the closest point count supplying copiousness value is 9 kilometer ; such distance might transcend the foraging radius of corvids and hence our copiousness index might be non as representative of the marauder copiousness environing the nests as we would anticipate. Finally, we have no information about the copiousness of mammal nest marauders, peculiarly with respects to squirrels which are known to feed upon eggs left unattended ( Murton 1965, Murton and Isaacson 1964 ) .
Contrary to our anticipation, monthly precipitation sum was non selected into concluding theoretical accounts to explicate fluctuation in nest endurance. Colombides nest are slackly built construction which are known to be vulnerable to adverse conditions conditions such as strong air currents and heavy precipitations ( refXXXX ) . The monthly sum of precipitation may be non a good altered step of such conditions and farther surveies should instead utilize hebdomadal at least sum along with air current strength in order to better take into history inauspicious conditions.
On another manus, mean monthly minimum temperature appeared to significantly impact on nest endurance during incubation. This factor ranked foremost after nesting habitat consequence ( incline 0.13 ) among all environmental factors included in the concluding theoretical account. To our cognition, no big graduated table surveies had already analysed the impact of such factor on nest endurance. Low temperature can impact incubation success either straight by chilling unattended eggs and decelerating embryo development ( Haftorn 1988 ) , or indirectly by increasing grownup metabolic activity required to keep organic structure temperature ( Conway and Martin 2000a, B ) , and hence changing the turns length at nest and the frequence of scrounging trips ( Conway and Martin 2000a, B ) . Increased metabolic costs may take grownups to go forth more frequently the nest in order to refill their organic structure shops, doing the nest more vulnerable to marauders or inauspicious conditions conditions. Temperatures could therefore constitute one of the most important bound on nest success in the first portion of engendering season. Again, nesting home grounds might be non all equivalents with regard to such restraint since urban country may bring forth a heater microclimate, compared to other rural home grounds ( Luniak et al 1990, Sukopp 1998 ) . Urban birds would so profit from faster embryo and chick growing, and therefore cut down the exposure period where they are accessible to nest marauders. Urban birds can besides get down engendering earlier, and it has already been noted that woodpigeons start engendering in metropolis Centres 8-10 yearss earlier than in rural country and complete the broods slightly subsequently ( Tomialojc 1980 ) .
Woodpigeon population copiousness
Nest endurance was non linked with population copiousness. Despite the steady addition in woodpigeon copiousness, no denseness dependance consequence was detected on nest endurance, proposing that population copiousness has non reached yet a impregnation threshold. Because we did non included theoretical accounts with interaction between variables, we can non nevertheless govern out possible consequence of copiousness in specific home ground. Such probe remains to be done, peculiarly in home grounds where big fluctuations in copiousness values are fund, like urban and farmland home grounds.
Our survey put into grounds that proximal home ground is the chief factor driving nest endurance rate in woodpigeon population, good in front scrounging home grounds and other environmental variables. Such consequence appears really consistent over clip and infinite, and at big spacial graduated table. Although it is ab initio alluring to first associate such differences between home grounds to difference in predation rate, our consequences suggest that the impact of predation on nest survival fluctuation is non every bit powerful as we expected, at least in a spacial position. However we acknowledge that this point merit more analysis since our proxi of predation force per unit area needs to be improved. Further, our informations do non enable us to deduce about the effect of temporal fluctuation in predation force per unit area on nest endurance. Yet, we think that our consequences are in understanding with remarks made by Martin and Clobert ( 1996 ) proposing that life-history traits might be driven chiefly by nutrient.
We voluntarily used a decreased figure of variables in our analysis, potentially embracing chief possible factors moving on nest endurance. However, in both genteelness phases, and peculiarly in the cuddling one, nest endurance was besides related to latitude and longitude, which gives no functional account by itself but suggests that a staying portion of fluctuation in nest endurance is explained by other spatially structured factors non considered in this survey.
Urban woodpigeon populations show much higher nest endurance rates than in any other nesting home ground. These higher values may ensue from lower predation force per unit area, propinquity of nutrient resources since a bulk of metropoliss are surrounded by big cultivated countries, and more favorable climatic conditions. In the context of the dramatically addition in populations observed over the stopping points decennaries, this consequence raises the inquiry of the part of the urban population into the whole woodpigeon population. Urban populations can exhibit a demographic excess, moving as a beginning of persons within a regional web of local populations ( Dias 1996 ) . Tomialojc ( 1980 ) argued that a high out-migration of immature hatched in urban Parkss is indispensable, as a effect of a really high production of immature and coincident deficiency of uninterrupted addition in Numberss of these populations. Radio-tracking informations besides show that woodpigeon born in urban topographic points can get down to engender in next agricultural countries ( unpublished information ) . Yet, nest endurance estimations provide merely one piece of the mystifier with respect to understanding the moral force of urban bird populations. Information on the figure of clasps laid each season, juvenile and grownup mortality, out-migration and in-migration rates is necessary before decisions can be drawn confidently about whether populations are self-sustaining within the urban environment. Similarly, whether lower nest endurance in rural home grounds is sufficient to make “ sink populations ” remains to be proved because it depends on the endurance of juveniles and grownups in the different home grounds. If any of the critical rates mentioned above are under density-dependent control, consequences of increased nest endurance and farther nest success may be counterbalanced by decrease in another critical rate.
Woodpigeon productiveness is potentially capable to much fluctuation since birds are able to rise up multiple broods ( up to 5 ) and bring forth replacing clasps rapidly after failure. Conversely, the instead fixed clasp size ( 2 biddies maximal ) limits the scope of productiveness per engendering effort. We suggest nevertheless that productiveness of urban woodpigeon population is likely to be higher than in other home grounds at least because of a longer urban genteelness season ( earlier start and subsequently stoping ) , giving more renesting chances. Our appraisal of nest endurance during the nestling phase does non take into history the period where juvenile woodpigeons are out of the nest but still dependent of parents to be fed. At this clip, birds fly really ill, and remain in the immediate locality of the nest, where they are still accessible to nest marauders. This period remains really ill studied mostly because of the deep colour and the close behavior of immature birds, doing hard to roll up perennial observations and to quantify their endurance. Consequently, estimations of spacial and temporal fluctuation form of generative productiveness, and the procedures that limit avian productiveness are frequently based purely on the figure of immature that are successfully fledged from the nest ( reviewed in Anders & A ; Marshall 2005 ) . Some surveies have shown that the factors act uponing the chance of nest success may non straight use to the post-fledging period ( Schmidt et al 2008 ) . For this ground, extrapolation of nesting informations for deducing population-level effects or ecological interactions will non be warranted. Consequently, our considerations about urban woodpigeon population kineticss need thorough surveies on post-fledging period, trusting either on radio-tracking informations and/or capture-recapture informations set on annular birds.
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