Spatial patterns of white stork (Ciconia ciconia) migratory phenology in the Iberian Peninsula

In contrast to the attention attracted by temporal trends of phenology, the spatial patterns of arrivals, departures or stays of trans-Saharan birds are still nowadays largely unknown in most of their European breeding areas. In the case of the white stork (Ciconia ciconia), some studies have attempted to describe its migratory patterns throughout some European countries but, to our knowledge, no one has related these patterns to some kind of explanatory variable which offers an ecologically-based explanation for the heterogeneous phenology observable among populations. Here, arrivals, departures and stays of this species, recorded in hundreds of Spanish localities, were related to a set of environmental, geographical, biological and spatial predictors, and modeled by multiple regression. The best model for arrival dates accounted for up to 34% of variability of data and pointed towards an earlier arrival in those populations located in south-western Iberia and with higher population densities. This last relationship is probably due to the competition for nest-site fidelity maintenance. However, no variable was able to explain properly the blurred spatial pattern recorded for departure dates. Departure decisions are strongly influenced by social behavior in this species and depend on collective decisions influenced by peculiar local environmental conditions of each year rather than macrogeographical gradients. Environmental, geographical or spatial variables also did not capture much of the observed variability in the length of the stays among populations. However, this variable was strongly related to the arrival and departure dates of populations. White storks stay longer in localities with earlier arrivals and, especially, later departures.     

Long-term satellite tracking of white stork ( Ciconia ciconia) migration: constancy versus variability

During satellite-tracking investigations of 140 white storks (Ciconia ciconia), one individual, the long-term world record holder among birds, was followed along 12 migratory journeys over a period of 10 years. This long-term study confirms what previous several-year tracking studies of white storks had indicated: there can be great variability from year to year in the choice of winter quarters as well as in the routes and times of migration, intermediate destinations and stop-over periods, but constancy of winter quarters and migration routes is also possible. The variability may well be caused by external factors, of which food supply is probably predominant.Communicated by F. Bairlein     

Census methods for White stork (Ciconia ciconia): bias in sampling effort related to the frequency and date of nest visits

Periodic censuses have been widely used to identify the population numbers and conservation status of many bird species. In order to be comparable, a census must be homogeneous through time. However, this requirement is not always possible. For this reason, studies addressing a possible bias in sampling efforts are very useful to correct such errors. In the present work, a standardized periodic monitoring of breeding White stork (Ciconia ciconia) at six Spanish colonies was conducted to estimate survey accuracy. We estimated the percentage of breeding pairs and productivity (number of chicks), i.e., accuracy, detected in each possible combination of number of visits as compared with the results obtained for the whole intensive monitoring, i.e., reality. Our results showed that single visits resulted in lower percentages of the number of breeding pairs and productivity detected compared with combinations of two or more visits. Nevertheless, one visit in a single month (April for the number of breeding pairs and June for productivity) did not show significantly lower results than the rest of the combinations of two or more visits. Early or late visits in the season might underestimate breeders by not accounting for either late-occupied or failed nests, respectively. In addition, the obvious increase in the probability of detection related with the number and the size of chicks is probably the reason why later visits in the season reported the highest value of productivity. In conclusion, the estimation bias presented in this study may be used to adjust sampling efforts in the census of the White stork.     

Effect of an ectoparasite on lay date, nest-site choice, desertion, and hatching success in the great tit (Pants major)

Ectoparasites are common in most bird species, but experimentalevidence of their effects on life-history traits is scarce.We investigated experimentally the effects of the hematophagoushen flea (Ceratophyllus gallinae) on timing of reproduction,nest-site choice, nest desertion, clutch size, and hatchingsuccess in the great tit (Parus major). When great tits wereoffered a choice on their territory between an infested anda parasite-free nest-box, they chose the one without parasites.When there was no choice, the great tits in a territory containingan infested nest-box delayed laying the clutch by 11 days ascompared with the birds that were offered a parasite-free nestingopportunity. The finding that there was no difference in phenotypictraits related to dominance between the birds nesting in infestedboxes and birds nesting in parasite-free boxes suggests thatthe delay is not imposed by social dominance. Nest desertionbetween laying and shortly after hatching was significandy higherin infested nests. There was no difference between infestedand parasite-free nests in clutch size, but hatching successand hence brood size at hatching were significantly smallerin infested nests. Nest-box studies of great tits have beenseminal in the development of evolutionary, ecological, andbehavioral theory, but recently a polemic has arisen in theliterature about the validity of the conclusions drawn fromnest-box studies where the naturally occurring, detrimentalectoparasites are eliminated by the routine removal of old nestsbetween breeding seasons. Our study suggests that this criticismis valid and that the evaluation of the effects of ectoparasitesmay improve our understanding of behavioral traits, life-historytraits, or population dynamics     

Low breeding success of the little egret (Egretta garzetta) near residential areas and in colonies exposed to gales: a comparison of colony in Sichuan,Southwest China,with literature

The breeding biology of the little egret (Egretta garzetta) was studied in 20 nests within the mixed-species breeding colonies at Nanchong, Sichuan, Southwest China, in 2006. By measuring a set of physical characteristics of vegetation at the nests and at a set of 20 randomly chosen sites we showed that birds preferentially used taller trees in areas with fewer shrubs of higher species diversity. Nests at lower locations in trees had marginally lower hatching success due to their destruction by humans; this destruction contributed marginally significantly to lowering of the total nesting success in all studied nests. Although gale winds also had a negative effect on breeding success, the anthropogenic influences were a greater factor in reproductive failure. We found similar effects in our review of literature on breeding success of the little egret from various geographical areas. Our results may be of use by conservation organizations in their actions to protect colonies of the little egret.     

越冬地东方白鹳繁殖生物学的初步研究

近年来,陆续在长江中下游越冬地发现东方白鹳(Ciconia boyciana)繁殖个体。为了了解该种在当地的繁殖对策和种群现状,2004-2006年在安庆市望江县武昌湖地区(116°51.15′-116°49.47′E,30°19.53′-30°19.79′N)对东方白鹳的繁殖生物学进行了研究。东方白鹳在当地开始营巢时间不一致,最早为2月5日,而受干扰的繁殖个体则延至5月6日。观察到的巢全在高压线塔上,巢高34.6±0.8m(n=11),巢间距908.8±1039.4m(n=6)。产卵期最早开始于2月11日,最晚6月21日,窝卵数4.2±0.4(4-5)枚(n=6)。育雏期71.0±16.1d(n=3),日育雏5.1±2.6(n=38),雏鸟离巢时间最早6月14日,最晚9月20日。2004和2005年东方白鹳在该地区共营巢8窝,产卵25枚,孵出雏鸟9只,出飞7只。繁殖失败5巢,其中,人工干扰造成4巢失败,高压电击毁1巢。繁殖不同时期,亲鸟的觅食、休息、警戒、取材、翻卵、育雏、交配、在巢、视野外行为时间分配差异显著,而飞翔、行走、理羽、击喙、整巢和其它行为差异不显著。雏鸟在发育的不同时期,觅食、飞翔、休息、整巢、在巢、行走、视野外行为时间分配差异显著,理羽、警戒、击喙和其它行为差异不显著     

Foraging behaviour and feeding success of the black-necked stork (Ephippiorhynchus asiaticus) in Dudwa National Park, Uttar Pradesh, India

Foraging behaviour of the black-necked stork (BNS) Ephippiorhynchus asiaticus was studied in 1996 and 1997 in Dudwa National Park (DNP), Uttar Pradesh, India. The storks were observed using tactile and visual techniques to catch fish. Of the 929 fish seen caught in 2 years, 894 (96%) were caught by a tactile mode of feeding and the remaining 35 (4%) by a visual mode of feeding. The rate of foraging attempts by BNS fluctuates with that of season in DNP and coincides with prey abundance. Immediately after the monsoon when the water level was high, BNS had to search for prey more often, as the prey became widespread. Whereas in summer when the water level decreased, the concentration of the fish was higher, which helps BNS to catch fish in quick succession. Prey behaviour and the condition of the wetland determined the selection of the tactile foraging technique among the BNS in DNP. The black-necked storks were more successful in the early hours of the day (06:00–10:00) and they were generally more successful or preferred to feed on medium-sized fish (i.e. 5–10 cm) in DNP. Prey profitability was highest for larger size fish and decreased as the prey size decreased. Principal component analysis showed that prey size, handling time of each prey, the month and water depth determined foraging success in 1996 and 1997.     

Relationship between clutch size,egg volume and hatching success in a Yellow-legged Gull Larus michahellis colony in south-eastern Tunisia

This study aimed to test the hypothesis that clutch size covaries with egg volume and hatching success in the Yellow-legged Gull Larus michahellis. We determined clutch size and egg volume in a sample of 131 nests, and we used the data to check whether egg volume varied among nests according to clutch size, while taking into account the effects of egg laying order. We also estimated hatching success rate and investigated the relationship between hatching success and clutch size. Egg volume varied among clutches according to clutch size, with eggs being larger in three-egg clutches than in two-egg clutches. Moreover, three-egg clutches showed higher daily survival rates, and hence hatching success, than two-egg clutches. Overall, our results suggest that in the Yellow-legged Gull clutch size covaries with egg volume and hatching success, which could possibly reflect an age effect through different mechanisms. Indeed, older females could be hypothesised to exhibit greater breeding performance than younger females because of their higher experience in tapping energy resources for egg formation and defending nests from dangers. Moreover, due to their age, older females are likely to have lower residual reproductive potential and should invest more heavily in current breeding attempts.     

The relationship between population means and variances of reproductive success differs between local populations of white stork (Ciconia ciconia)

We studied the size and productivity of white stork (Ciconia ciconia) populations in eight study sites in Poland. The number of nesting pairs and the average number of chicks fledged per pair fluctuated over time, and the studied populations differed in the variance of both breeding success and number of breeding pairs. The variance of breeding success (both for the mean number of chicks and the proportion of successful nests) and the variance of the number of breeding pairs was not correlated with the extent of stable habitats (pastures, meadows, wetlands), other habitats (farmland), or with local population trends over time. We found a non-linear symmetrical relationship between annual mean reproductive success and its variance but only when considered as the proportion of successful nests (i.e., when individual nests are coded as a binary value: 0, no success; 1, success). No such relationship existed when success was expressed as the number of fledged chicks. Although a positive significant correlation occurred between fledgling numbers (discrete data) and the proportion of successful nests (binary data), we believe that the use of only binary data will be inadequate in more detailed analyses, such as population viability analysis.     

Uphill shifts in the distribution of the white stork Ciconia ciconia in southern Poland: the importance of nest quality

The aim of this paper is to explain the altitudinal changes that have occurred during the 20th century to the white stork distribution in the Podhale region of the uplands of the Tatra mountains, southern Poland. We analysed both historical data from the white stork censuses and detailed yearly records from 1974 to 2003 on population size, distribution and breeding success. A white stork nest was first recorded at Podhale in 1931 and numbers increased to seven nests in 1933, all located below 650 m altitude. During the 30‐years, 1974–2003, both the maximum and upper‐quartile altitudes of nests increased significantly. In 1974 the highest nest was at an altitude of 770 m, and the maximum reached 890 m in 1999. In the same period, the breeding population increased significantly. The minimum and lower‐quartile altitudes of nests decreased significantly following initial occupation of suitable lower altitude sites before uphill expansion. We noted the positive association between nest occupancy over the study period and breeding performance. As a result, long‐occupied nests contributed most of the young produced in the population and chicks from these nests probably colonized new areas. We believe this is the first well‐documented evidence of, and mechanism for, a particular bird species to ascend to higher elevations and that the altitudinal shifts reported for butterflies, plants and whole biomes can be detected in birds as well.     

Light microscopy and scanning electron microscopy studies on the reduction of the tongue microstructures in the white stork (Ciconia ciconia,Aves)

The structure of the tongue in the white stork (Ciconia ciconia) is observed macroscopically and under light and scanning electron microscopy. Our observations of the tongue reveal a rare terminal reduction of the size of the tongue and microstructures of the lingual mucosa among the investigations of birds published so far. The short, triangular tongue with a pointed tip is approximately 2.5 cm long in the adult and is situated in the caudal part of the oral cavity close to the laryngeal prominence. On the dorsal surface of the tongue, no typical mucosa microstructures like lingual papillae, median groove or lingual prominence are observed. The main structure of the tongue is composed of rostral part of hyoid apparatus, that is, entoglossal cartilage connects with basihyoid. Very thin mucosa is composed of fibrous connective tissue covered with orthokeratinized epithelium. No lingual glands and muscles are observed in the lamina propria of mucosa. Even though the triangular shape of the tongue in the white stork is typical for birds, the inner structure of the reduced organ is composed only of flat cartilagineous entoglossum of hyoid apparatus. During feeding behaviour of the white stork, the food transportation in oral cavity called cranio‐inertial transport is undoubtedly affected by structural reduction of the tongue.     

Using Corine Land Cover Habitat Database for the analysis of breeding bird habitat: case study of white storks (Ciconia ciconia) from northern Croatia

The purpose of this study was to find out whether a set of habitat characteristics, derived from the National Corine Land Cover (CLC) database of habitat types, could indicate the occurrence of white stork nests in a settlement. The analyses were performed for the settlements closer than 35 km from the Drava River (northern Croatia). Sixteen habitat characteristics were determined around 257 settlements occupied with white stork nests and 152 control sites without white stork nests within the same geographic region. We performed multivariate inspection of the data and a non-metric multidimensional preference analysis. The best variables for stork habitat selection were: distance to the nearest grassland habitat (P < 0.0001), distance to three nearest grassland habitats (P < 0.0001), altitude of the settlements above the sea level (P < 0.001), sum of distances to the three nearest agricultural mosaic habitats (P < 0.005) and standardized area proportion of forests (P < 0.05). The explanatory capacity of the model was 81.1%. We conclude that it is possible to define a small number of habitat characteristics derived from CLC database which can indicate the occurrence of white stork nests.     

Magnetic resonance imaging and spectroscopy (MRI, MRS) of seasonal patterns of body composition: A methodological pilot study in White Storks (Ciconia ciconia)

Summary Here we present a systematic application of magnetic resonance imaging (in the following called MRI) and magnetic resonance spectroscopy (MRS) to the White Stork. The main aim was to demonstrate the annual cycle of fat deposition in the same individuals for comparison to wild conspecifics, to clarify the energy metabolism of this migratory species. To obtain sharp, high-contrast images of the interior of the body, the birds were kept still by enclosing them in simple plastic tubes with additional fixation of legs and head, avoiding the problematic sedation with drugs. Altogether 12 test birds (young storks) were monitored systematically for 15 months, to follow seasonal changes in the internal organs (mainly breast muscles) and tissues (mainly fat depots). At each examination 22 high-contrast pixel images representing serial dorsoventral sections through the body were generated with the computer program MatLab, after which the pixels per section image were converted to tissue components in cm² and the distances between consecutive sections used to calculate the tissue volumes in cm³. To measure the fat in the breast muscle spectroscopy was used to determine the fat : water ratio, from which changes in fat content could be derived. The study revealed pronounced seasonal changes in the visceral and cutaneous/subcutaneous fat depots, which precisely paralleled the annual variation in body weight of the birds (see also the preceding paper, Berthold et al. 2001). The breast muscles exhibited the prolonged growth typical of the juveniles of large species but no conspicuous change at the migration periods. In this project MRI and MRS proved to be successful methods that show great promise.

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Magnet-Resonanz-Tomographie und -Spektroskopie der jahreszeitlichen Muster der Körperzusammensetzung: Eine methodische Pilotstudie am Weißstorch (Ciconia ciconia)

Zusammenfassung In der vorliegenden Arbeit stellen wir eine systematische Anwendung der Magnet-Resonanz-Tomographie (Kernspin-Tomographie, im Folgenden MRT) und der Magnet-Resonanz-Spektroskopie (im Folgenden MRS) am Weißstorch vor. Hauptaufgabe war es, die Jahresperiodik der Fettdeposition an denselben Individuen zu ermitteln, um Aufschluss über den Energiehaushalt dieser Zugvogelart durch Vergleiche mit freilebenden Vögeln zu bekommen. Die erforderliche Ruhigstellung der Vögel zum Erreichen scharfer kontrastreicher Bilder des Körperinneren war in einfachen Plastikröhren mit zusätzlicher Fixierung von Beinen und Kopf möglich, so dass auf die problematische Sedierung mit Narkotika verzichtet werden konnte. Insgesamt 12 Versuchsvögel (Jungstörche) wurden 15 Monate lang systematisch auf jahresperiodische Veränderungen von inneren Organen (v. a. Brustmuskeln) und Geweben (v. a. Fettdepots) untersucht. Aus je 22 seriellen kontrastreichen dorsoventralen Schnittbildern durch den Vogelkörper ließen sich mit dem Computerprogramm MatLab Pixelbilder erstellen und dann die Pixel pro Schnittbild in Gewebeanteile in cm² umrechnen und anschließend aus den aufeinander folgenden Schnittbildern die Gewebevolumina in cm³ ermitteln. Für die Fettbestimmung im Brustmuskel wurde durch Spektroskopie das Verhältnis von Fett: Wasser bestimmt, aus dem Veränderungen des Fettgehalts abgeleitet wurden. Die Studie ergab ausgeprägte jahresperiodische Änderungen der viszeralen und kutanen/subkutanen Fettdepots, die genau parallel zum Jahresgang des Körpergewichts der Vögel verliefen (s. auch die vorangehende Arbeit, Berthold et al. 2001). Für die Brustmuskeln ergab sich ein für Jungvögel großer Arten typisches lang anhaltendes Wachstum, aber keine auffallende Veränderung zu den Zugperioden. MRT und MRS erwiesen sich in dieser Arbeit als erfolgreich und vielversprechend.

     

Climate and spatio-temporal variation in the population dynamics of a long distance migrant, the white stork

1. A central question in ecology is to separate the relative contribution of density dependence and stochastic influences to annual fluctuations in population size. Here we estimate the deterministic and stochastic components of the dynamics of different European populations of white stork Ciconia ciconia. We then examined whether annual changes in population size was related to the climate during the breeding period (the 'tap hypothesis' sensu Saether, Sutherland & Engen (2004, Advances in Ecological Research, 35, 185 209) or during the nonbreeding period, especially in the winter areas in Africa (the 'tube hypothesis'). 2. A general characteristic of the population dynamics of this long-distance migrant is small environmental stochasticity and strong density regulation around the carrying capacity with short return times to equilibrium. 3. Annual changes in the size of the eastern European populations were correlated by rainfall in the wintering areas in Africa as well as local weather in the breeding areas just before arrival and in the later part of the breeding season and regional climate variation (North Atlantic Oscillation). This indicates that weather influences the population fluctuations of white storks through losses of sexually mature individuals as well as through an effect on the number of individuals that manages to establish themselves in the breeding population. Thus, both the tap and tube hypothesis explains climate influences on white stork population dynamics. 4. The spatial scale of environmental noise after accounting for the local dynamics was 67 km, suggesting that the strong density dependence reduces the synchronizing effects of climate variation on the population dynamics of white stork. 5. Several climate variables reduced the synchrony of the residual variation in population size after accounting for density dependence and demographic stochasticity, indicating that these climate variables had a synchronizing effect on the population fluctuations. In contrast, other climatic variables acted as desynchronizing agents. 6. Our results illustrate that evaluating the effects of common environmental variables on the spatio-temporal variation in population dynamics require estimates and modelling of their influence on the local dynamics.     

Effects of oxygen,carbon dioxide,and nitrogen on hatching behavior and hatching time in the katydid,Eobiana engelhardti subtropica Bey-Bienko (Orthoptera: Tettigoniidae)

The trigger for the hatching behavior and determination of hatching time of the katydids, Eobiana engelhardti subtropica (Orthoptera: Tettigoniidae) have been shown to be influenced by light–dark signals or temperature. In this study, I investigated the effects of oxygen, carbon dioxide, and nitrogen on the hatching behavior and hatching time of the katydid. Eggs rarely hatched under a constant temperature of 25°C and hatched sporadically at a constant temperature of 15°C under continuous light in the air. However, when eggs were exposed to 100% oxygen or a mixture of oxygen and nitrogen (2:1 or 1:1), hatching occurred within a few seconds. Hatching behavior was directly triggered by high concentrations of oxygen. It was inhibited by exposure to 100% carbon dioxide, 100% nitrogen, or a mixture of oxygen and nitrogen (1:2). The hatching time, determined by the temperature fall (transfer from 25°C to 15°C), was delayed by these gases, and was reset by the transfer back of eggs to the air. This suggests the existence of a time-measuring mechanism that is triggered by the transfer of eggs to the air. These results, indicating that hatching behavior was directly triggered by high concentrations of oxygen and that hatching time was set by the transfer from carbon dioxide or nitrogen to the air, are new findings to the best of my knowledge.     

扬子鳄(Alligator sinensis)卵体积和重量估算及其对孵化成功率的影响

收集了安徽省扬子鳄国家级自然保护区2004、2006、2007年的800枚扬子鳄卵和2007年的188条幼鳄的相关数据.经统计分析,得到卵的体积、重量的回归方程(V=0.537LB2 1.151,R2=0.960;W=0.593LB2-0.541,R2=0.975)和估算公式(V=0.553LB2,F=0.267,P=0.606＞0.05;W=0.585LB2,F=0.003,P=0.960＞0.05).公式V=0.553LB2 估算出的卵的体积与实际体积相比,误差小于3%;公式W=0.585LB2估算的卵的重量与实际鲜重相比,误差小于2%.基于卵的体积和重量推导公式,还探讨卵的体积、重量与孵化成功率和繁殖成功率之间的关系,结果表明,扬子鳄卵的体积、重量对孵化成功率和繁殖成功率均有明显的影响,较大的卵孵化出幼鳄的几率及成活率都更高.     

Drivers of the breeding success of American Oystercatchers (Haematopus palliatus frazari) at a critical site in Sinaloa,Mexico

Understanding breeding phenology and success can elucidate population dynamics, which is especially important for species in need of conservation. We describe the factors affecting the breeding biology of American Oystercatchers (Haematopus palliatus frazari) at El Rancho Island, a critical site that contains ~ 7% of the total estimated population, on the coast of Sinaloa, Mexico. We monitored 192 nests over four years (2016–2019). The breeding season lasted from March to June and mean laying dates differed among years, with the mean laying date in 2019 an average of 20 days earlier than in 2016. Clutch sizes decreased as the breeding season progressed. Both breeding success and productivity differed among years, with the lowest values in 2016 (30% hatching success and 0.6 chicks/nest) and the highest in 2019 (66% hatching success and 1.2 chicks/nest). Hatching success was affected by year, laying date, type of habitat, and distance to the high tide line. American Oystercatchers that laid eggs earlier in the season, used mixed marsh and dune habitat, and with nests relatively close to the waterline (< 50 m) had greater breeding success. Overall, however, the breeding success of American Oystercatchers was low and influenced by a combination of several intrinsic and extrinsic factors. Management measures may be required to increase breeding success and ensure the conservation of this subspecies.     

Nest position,breeding success and diet of the Black-crowned Night Heron,Nycticorax nycticorax in the Anzali Wetland,Northern Iran (Aves: Ardeidae)

Breeding ecology of the Black-crowned Night Heron (Nycticorax nycticorax) was studied in a mono-specific colony in the Anzali wetland, Northern Iran during the breeding season of 2016. The breeding period lasted from mid-May to late July. The average clutch size was 3.1±0.6 eggs and the breeding success 77.6%. No significant differences were found between nests built on trunks and those built on branches of trees. The clutch size and breeding success appeared to be independent of the structural variables of the nesting site (diameter of trees, height from the ground, height of nests from the canopy, nest number per tree, location of nests on trunks and branches). No significant difference was found between the timing of the start of incubation and the height of nests above the ground. The average vertical and horizontal distances between nests was one metre. Fish, particularly Carassius gibelio, dominated the diet of the nestlings.     

Colour composition of nest lining feathers affects hatching success of barn swallows,Hirundo rustica (Passeriformes: Hirundinidae)

Many bird species use feathers as lining material, and its functionality has traditionally been linked to nest insulation. However, nest lining feathers may also influence nest detection by predators, differentially affect reproductive investment of mates in a post‐mating sexual selection process, and affect the bacterial community of the nest environment. Most of these functions of nest lining feathers could affect hatching success, but the effect might vary depending on feather coloration (i.e. pigmented versus white feathers). This would be the case if coloration is related to: (1) thermoregulatory properties; (2) attractiveness of feathers in the nest for mates; (3) eggshell bacterial density. All of these hypothetical scenarios predict that feathers of different colours would differentially affect the hatching success of birds, and that birds should preferentially choose the most beneficial feather colour for lining their nests. Results from two different experiments performed with a population of Danish barn swallow, Hirundo rustica, were in accordance with these predictions. First, H. rustica preferentially selected white experimentally offered feathers for lining their nests. Second, the experimental manipulation of the feather colour composition of nests of H. rustica had a significant effect on hatching success. Experimental nests with more white feathers added at the beginning of incubation had a lower probability of hatching failures, suggesting differential beneficial effects of lining nests with feathers of this colour. We discuss the relative importance of hypothetical functional scenarios that predicted the detected associations, including those related to sexual selection or to the community of microorganisms associated with feathers of different colours. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 67–74.     

Climatic effects on the breeding phenology and reproductive success of an arctic-nesting goose species

Climate warming is pronounced in the Arctic and migratory birds are expected to be among the most affected species. We examined the effects of local and regional climatic variations on the breeding phenology and reproductive success of greater snow geese ( Chen caerulescens atlantica ), a migratory species nesting in the Canadian Arctic. We used a long-term dataset based on the monitoring of 5447 nests and the measurements of 19 234 goslings over 16 years (1989–2004) on Bylot Island. About 50% of variation in the reproductive phenology of individuals was explained by spring climatic factors. High mean temperatures and, to a lesser extent, low snow cover in spring were associated with an increase in nest density and early egg-laying and hatching dates. High temperature in spring and high early summer rainfall were positively related to nesting success. These effects may result from a reduction in egg predation rate when the density of nesting geese is high and when increased water availability allows females to stay close to their nest during incubation recesses. Summer brood loss and production of young at the end of the summer increased when values of the summer Arctic Oscillation (AO) index were either very positive (low temperatures) or very negative (high temperatures), indicating that these components of the breeding success were most influenced by the regional summer climate. Gosling mass and size near fledging were reduced in years with high spring temperatures. This effect is likely due to a reduced availability of high quality food in years with early spring, either due to food depletion resulting from high brood density or a mismatch between hatching date of goslings and the timing of the peak of plant quality. Our analysis suggests that climate warming should advance the reproductive phenology of geese, but that high spring temperatures and extreme values of the summer AO index may decrease their reproductive success up to fledging.