Spring Arrival Research Articles

Has climate change resulted in a mismatch between the spring arrival of the Common Cuckoo Cuculus canorus and its hosts in North Norway?

Analysis of spring arrival dates in North Norway showed advanced arrival of the Common Cuckoo Cuculus canorus but not of four of its most frequently used hosts. No evidence was found of a climate-driven mismatch that might contribute to the decline in the Norwegian Cuckoo population. Normal 0 false false false NO-BOK X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Vanlig tabell; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-fareast-language:EN-US;}

Spatio-temporal Trend Analysis of Spring Arrival Data for Migratory Birds

There is increasing interest in spatio-temporal analysis of environmental and ecological responses to changes in the climate due to the recent concerns about climate change. In this work, we propose a spatio-temporal modeling framework for analyzing environmental and ecological data while accounting for spatial and temporal structure, as well as climate effects. As an example, we consider data on bird migration in the United States and analyze the spring arrival dates of Purple Martins between historical data (1905–1940) from the North American Bird Phenology Program and recent data (2001–2010) from the Purple Martin Conservation Association. The proposed approach allows researchers to compare mean arrival dates while accounting for spatial and temporal variability. Our results for Purple Martins showed statistically significant earlier spring arrivals in parts of United States over the recent years. The proposed approach provides a useful tool for statistical analysis of spatio-temporal data related to studies of climate change.

Wing length and age, but not tarsus or mass, independently determine spring arrival at breeding territories in a long-distance migrant the Common Whitethroat, Sylvia communis

Capsule Wing length and age independently predicted spring arrival timing in a long-distance migratory warbler, but there was no association with mass or tarsus length.Aims To test a range of biometric features and other measures of fitness for their importance in determining spring arrival patterns in a long-distance migratory landbird, and to investigate why these features may be important.Methods Fifty-one males with known spring arrival dates were caught and key biometrics were measured at breeding sites across Norfolk, UK, during April and May 2012. Blood samples were also taken in order to consider any effect of infection with blood parasites.Results Early-arriving males were more likely to be adults and to have longer wings. Mass and tarsus length had no significant relationship with arrival timing. Haemosporidian prevalence was low (∼10%) compared to other studies of this species, and so it was not possible to determine the effect of infection on arrival date with confidence.Conclusions Wing length, rather than other measures that simply measure structural body size, is probably important in arrival timing due to either the advantage it confers by increasing flight efficiency or because it reflects past condition during feather growth.

Spatial patterns of goose grubbing suggest elevated grubbing in dry habitats linked to early snowmelt

The western Palaearctic tundra is a breeding habitat for large populations of European geese. After their arrival in spring, pink-footed geese ( Anser brachyrhynchus ) forage extensively on below-ground plant parts, using a feeding technique called grubbing that has substantial impact on the tundra vegetation. Previous studies have shown a high frequency of grubbing in lowland fen vegetation. In the present study, we examined the occurrence of grubbing in other habitat types on Spitsbergen, in the Arctic archipelago of Svalbard. Goose grubbing was surveyed along 19 altitudinal transects, going from the valley bottom to altitudes dominated by scree. Grubbing was more frequent in the wet habitat type at low altitudes compared to the drier habitat type at higher altitudes. For the dry habitat type, a higher frequency of grubbing was found in study plots with a south-east facing exposure where snowmelt is expected to be early. This suggests that pink-footed geese primarily use dry vegetation types for grubbing when they are snow-free in early spring and the availability of snow-free patches of the preferred wet vegetation types in the lowlands is limited. Dry vegetation types have poorer recovery rates from disturbance than wet ones. Sites with early snowmelt and dry vegetation types may therefore be at greater risk of long-term habitat degradation. We conclude that the high growth rate of the Svalbard-breeding pink-footed goose population suggests that increasing impacts of grubbing can be expected and argue that a responsible monitoring of the effects on the tundra ecosystem is crucial. Keywords: Anser brachyrhynchus ; grubbing; habitat; pink-footed goose; Svalbard; tundra (Published: 29 May 2013) Citation: Polar Research 2013, 32 , 19719, http://dx.doi.org/10.3402/polar.v32i0.19719

Changes in climate and weather parameters and their correlation with spring arrival of the common crane (Grus grus) in northern Moscow region

Changes in climate and weather parameters and their correlation with spring arrival of the common crane (<i>Grus grus</i>) in northern Moscow region

Drought in Africa Caused Delayed Arrival of European Songbirds

Despite an overall advancement in breeding area arrival, one of the latest spring arrivals in northwest Europe since 1950 of several trans-Saharan songbird species occurred in 2011. Year-round tracking of red-backed shrikes and thrush nightingales revealed that the cause of the delay was a prolongation of stopover time during spring migration at the Horn of Africa, which was affected by extreme drought. Our results help to establish a direct link at the individual level between changes in local climate during migration and arrival and breeding condition in Europe thousands of kilometers further north.

Influence of Climate Change on Avian Migrants' First Arrival Dates

Abstract. Long-term studies over a variety of regions, species, and time periods can help link trends in climate to changes in bird phenology and provide better understanding of potential effects of climate change. We analyzed first spring arrival dates of 93 species of migrants from the Buffalo Ornithological Society's database covering the period from 1967 to 2008. Migrants appeared a mean 0.10 days earlier each year. Short-range migrants, traveling from a winter range within North America, have advanced their average arrival more, 0.15 days per year, than have long-range migrants from Central America, South America, or the West Indies, whose advance averaged 0.06 days per year. We regressed arrival dates against the temperature of short-range migrants' winter range, as represented by Houston, Texas, and the North American Oscillation Index as indicators of climate change. The Houston temperature correlates well with earlier arrival dates, especially for short-range migrants. We compared our results wit...

Range-wide effects of breeding- and nonbreeding-season climate on the abundance of a Neotropical migrant songbird

Geographic variation in the population dynamics of a species can result from regional variability in climate and how it affects reproduction and survival. Identifying such effects for migratory birds requires the integration of population models with knowledge of migratory connectivity between breeding and nonbreeding areas. We used Bayesian hierarchical models with 26 years of Breeding Bird Survey data (1982-2007) to investigate the impacts of breeding- and nonbreeding-season climate on abundance of American Redstarts (Setophaga ruticilla) across the species range. We focused on 15 populations defined by Bird Conservation Regions, and we included variation across routes and observers as well as temporal trends and climate effects. American Redstart populations that breed in eastern North America showed increased abundance following winters with higher plant productivity in the Caribbean where they are expected to overwinter. In contrast, western breeding populations showed little response to conditions in their expected wintering areas in west Mexico, perhaps reflecting lower migratory connectivity or differential effects of winter rainfall on individuals across the species range. Unlike the case with winter climate, we found few effects of temperature prior to arrival in spring (March-April) or during the nesting period (May-June) on abundance the following year. Eight populations showed significant changes in abundance, with the steepest declines in the Atlantic Northern Forest (-3.4%/yr) and the greatest increases in the Prairie Hardwood Transition (4%/yr). This study emphasizes how the effects of climate on populations of migratory birds are context dependent and can vary depending on geographic location and the period of the annual cycle. Such knowledge is essential for predicting regional variation in how populations of a species might vary in their response to climate change.

Effect of atmospheric circulation types on spring arrival of migratory birds and long-term trends in the first arrival dates in Estonia

We studied the spring arrival of 42 migratory bird species in Estonia in relation to integrated climatological variables (atmospheric circulation types). We found that all early arrivals were short- distance migrants, which were more directly affected by cyclonic conditions. Those conditions design a tailwind system that favours or hinders the migration of birds to their breeding areas. All late arrivals were long-distance migrants, whose spring arrival took place mostly in anti-cyclonic windless or also eastern or south-eastern wind conditions, i.e. tail- or crosswinds. Our hypothesis that different arrival times of the same species in western (Kuressaare) and eastern (Tartu) Estonia may have been caused by the birds' different circulation type preferences was not confirmed - birds preferred similar types. Differences in the first arrival dates between western and eastern Estonia were related rather to climatic differences as well as differences in flyways and migratory routes. The spring arrival date significantly advanced during the period 1958-2002 in several species from both guilds but the rate and significance of the advances were in general higher in early arrivals than in late arrivals. We concluded that weather conditions and climate change affected the spring arrival of both short-distance and long-distance migrants. Among circulation classifications, the effects on migratory birds were most often detected in the case of classifications with a low number of circulation types (such as SANDRAS or CKMEANSC09), suggesting that birds are generally not waiting for very specific types of circulation. The results indicate that methods of synoptic climatology are useful for studying bird migration phenology and migration patterns, especially at a large scale.

Ecological conditions in wintering and passage areas as determinants of timing of spring migration in trans-Saharan migratory birds

1. Climate change has been associated with shifts in the timing of biological events, including the spring arrival of migratory birds. Early arrival at breeding sites is an important life-history trait, usually associated with higher breeding success and therefore, susceptible to selection and evolution in response to changing climatic conditions. 2. Here, we examine the effect of changes in the environmental conditions of wintering and passage areas on the mean passage time of 13 trans-Saharan passerines during their spring migration through the western Mediterranean over the 15 years from 1993 to 2007. 3. We found that most of the species studied have been advancing the timing of their passage in recent years. However, annual variation in the mean date of passage was positively correlated with vegetation growth (measured as the normalized difference vegetation index [NDVI]) both in the Sahel (the region of departure) and in northern Africa (the passage area). Thus, migration dates were delayed in years with high primary productivity in passage and wintering zones. All species seem to respond similarly to NDVI in the Sahel; however, late migrants were less affected by ecological conditions in northern Africa than those migrating earlier, suggesting differences based on species ecology. 4. Mean timing of passage was not related to the North Atlantic Oscillation (NAO), El Niño-Southern Oscillation (ENSO), temperature or NDVI in the species-specific wintering areas (the overwintering region) when analysed in combination with the other covariates. 5. Our findings show that ecological conditions in the winter quarters (specifically the Sahel) and en route are relevant factors influencing trends in the passage dates of trans-Saharan migratory birds on the southern fringe of Europe. Possible long-term consequences for late arriving spring migrants are discussed.

Effects of Climate Change on Spring Arrival Times of Birds in Thoreau's Concord From 1851 TO 2007

Abstract. The effects of climate change have been detected in numerous biological systems. Study of phenology, including the timing of bird migrations, has proven to be an effective tool for understanding the degree to which plants and animals are affected by climate change. In this study, we analyzed records of birds' arrival at Concord, Massachusetts, over 157 years, compiling the longest known record of bird-arrival dates in North America. Using records of bird arrivals by American philosopher and naturalist Henry David Thoreau for 1851–1854 and the well-known ornithologists William Brewster for 1886 and 1900–1919 and Ludlow Griscom for 1930–1931 and 1933–1954, we examined whether birds are shifting their arrival times in response to a warming climate. Concord resident Rosita Corey provided a set of recent observations for the years 1956–1973 and 1988–2007. When we considered all 22 species of migratory songbirds we analyzed together, we found no average change in arrival date over time, though when we...

Life history events of the Eurasian sparrowhawk Accipiter nisus in a changing climate

Current climate change has been found to advance spring arrival and breeding dates of birds, but the effects on autumn migration and possible responses in the distribution of wintering individuals are poorly known. To thoroughly understand the consequences of climate change for animal life histories and populations, exploration of whole annual cycles are needed. We studied timing of migration (years 1979–2007), breeding phenology (1979–2007) and breeding success (1973–2007) of Eurasian sparrowhawks Accipiter nisus in Finland. We also investigated whether the migration distance of Finnish sparrowhawks has changed since the 1960s, using ringing recovery records. Since the late 1970s Finnish sparrowhawks have advanced their spring arrival, breeding and autumn departure considerably, but the migration distance has not changed. Early migrants, who are the ones with the highest reproductive success, show the strongest advance in the timing of spring migration. In autumn, advanced departure concerns young sparrowhawks. Late autumn migrants, who are mainly adults, have not advanced their migration significantly. The sparrowhawk is the most common bird of prey and the main predator of most passerines in Finland. Therefore, changes in sparrowhawk migration phenology may affect the migration behaviour of many prey species. The breeding success of sparrowhawks has increased significantly over the study period. This is however more likely caused by other factors than climate change, such as reduced exposure to organochlorine pollutants.

Local Temperature Fine-Tunes the Timing of Spring Migration in Birds

Evidence for climate-driven phenological changes is rapidly increasing at all trophic levels. Our current poor knowledge of the detailed control of bird migration from the level of genes and hormonal control to direct physiological and behavioral responses hampers our ability to understand and predict consequences of climatic change for migratory birds. In order to better understand migration phenology and adaptation in environmental changes, we here assess the scale at which weather affects timing of spring migration in passerine birds. We use three commonly used proxies of spring-time climatic conditions: (1) vegetation "greenness" (NDVI) in Europe, (2) local spring temperatures in northern Europe, and (3) the North Atlantic Oscillation Index (NAO) as predictors of the phenology of avian migration as well as the strength of their effect on different subsets of populations and the dependence of correlations on species-specific migratory strategy. We analyze phenological patterns of the entire spring migration period in 12 Palaearctic passerine species, drawing on long-term data collected at three locations along a longitudinal gradient situated close to their northern European breeding area. Local temperature was the best single predictor of phenology with the highest explanatory power achieved in combination with NAO. Furthermore, early individuals are more affected by climatic variation compared to individuals on later passage, indicating that climatic change affects subsets of migratory populations differentially. Species wintering closer to the breeding areas were affected more than were those travelling longer distances and this pattern was strongest for the earliest subsets of the population. Overall, our results suggest that at least early subsets of the population are affected by local conditions and early birds use local conditions to fine-tune the date of their spring arrival while individuals arriving later are driven by other factors than local conditions e.g. endogenous control. Understanding what cues migratory organisms use to arrive at an optimum time is important for increasing our knowledge of fundamental issues like decision making in organisms during migration and is crucial for future protection of migratory organisms.

Avian population consequences of climate change are most severe for long-distance migrants in seasonal habitats

One consequence of climate change is an increasing mismatch between timing of food requirements and food availability. Such a mismatch is primarily expected in avian long-distance migrants because of their complex annual cycle, and in habitats with a seasonal food peak. Here we show that insectivorous long-distance migrant species in The Netherlands declined strongly (1984-2004) in forests, a habitat characterized by a short spring food peak, but that they did not decline in less seasonal marshes. Also, within generalist long-distance migrant species, populations declined more strongly in forests than in marshes. Forest-inhabiting migrant species arriving latest in spring declined most sharply, probably because their mismatch with the peak in food supply is greatest. Residents and short-distance migrants had non-declining populations in both habitats, suggesting that habitat quality did not deteriorate. Habitat-related differences in trends were most probably caused by climate change because at a European scale, long-distance migrants in forests declined more severely in western Europe, where springs have become considerably warmer, when compared with northern Europe, where temperatures during spring arrival and breeding have increased less. Our results suggest that trophic mismatches may have become a major cause for population declines in long-distance migrants in highly seasonal habitats.

Spring migration phenology of birds in the Northern Prairie region is correlated with local climate change

ABSTRACT In apparent response to recent periods of global warming, some migratory birds now arrive earlier at stopover sites and breeding grounds. However, the effects of this warming on arrival times vary among locations and species. Migration timing is generally correlated with temperature, with earlier arrival during warm years than during cold years, so local variation in climate change might produce different effects on migration phenology in different geographic regions. We examined trends in first spring arrival dates (FADs) for 44 species of common migrant birds in South Dakota (1971–2006) and Minnesota (1964–2005) using observations compiled by South Dakota and Minnesota Ornithologists’ Unions. We found significant trends in FAD over time for 20 species (18 arriving earlier and two later) in South Dakota and 16 species (all earlier) in Minnesota. Of these species, 10 showed similar significant trends for both states. All 10 of these species exhibited significantly earlier arrival, and all were early spring migrants, with median FADs before 10 April in both states. Eighteen of the 44 species showed significant negative correlations of FADs with either winter (December–February) or spring (arrival month plus previous month) temperatures in one or both states. Interestingly, spring temperatures in both South Dakota and Minnesota did not warm significantly from 1971–2006, but winter temperatures in both states warmed significantly over the same time period. This suggests that the warmer winters disproportionately affected early spring migrants, especially those associated with aquatic habitats (seven of the 10 species showing significantly earlier spring arrival in both states). The stronger response to climate change by early spring migrants in our study is consistent with the results of several other studies, and suggests that migrants, especially early migrants, are capable of responding to local temperature conditions experienced on wintering grounds or along the migration route. En una respuesta aparente a recientes periodos de calentamiento global, algunas aves migratorias actualmente están arribando más temprano en los lugares de paradas y zonas de reproducción. Sin embargo, el efecto de este calentamiento sobre los tiempos de llegada varia entre localidades y especies. El inicio de la migración esta generalmente correlacionado con la temperatura, con llegadas tempranas durante años cálidos que en los años fríos, entonces variación local en cambios climáticos puede producir diferentes efectos en la fenología de migración en diferentes regiones geográficas. Examinamos tendencias en la fecha de la primera llegada primaveral (FPLL) para 44 especies de migrantes comunes en South Dakota (1971–2006) y Minnesota (1964–2005) usando observaciones acumuladas por la unión de ornitólogos de South Dakota y Minnesota. Encontramos tendencias significativas en FPLL a través del tiempo para 20 especies (28 llegaron temprano y dos tarde) en South Dakota y 16 especies (todas temprano) en Minesota. De estas especies, 10 mostraron tendencias significativas similares en ambos estados. Todas de las 10 especies exhibieron una llegada significativamente temprana, y todos fueron migrantes primaverales tempranos, con una media de FPLL antes del 10 de abril en ambos estados. Dieciocho de estas 44 especies mostraron una correlación negativa significativa en FPLL de manera similar en las temperaturas de invierno (Diciembre-Febrero) o primavera (mes de arribo más el mes anterior) en uno o ambos estados. Interesantemente, temperaturas de primavera en ambos South Dakota y Minnesota no se calentaron significativamente entre 1971–2006, pero temperaturas invernales en ambos estados se calentaron significativamente durante el mismo periodo de tiempo. Esto sugiere que los inviernos calientes afectan de manera desproporcional la llegada temprana de migrantes durante la primavera, especialmente los asociados con hábitat acuáticos (siete de las 10 especies mostraron una llegada significativamente mas temprana en la primavera en ambos estados). La fuerte respuesta a cambio climático por aves migrantes durante la primavera en nuestro estudio es consistente con los resultados de varios estudios y sugiere que migrantes, especialmente migrantes tempranos, son capaces de responder a condiciones locales de temperaturas experimentadas en las zonas de invierno o a lo largo de la ruta de migración.

Spring arrival along a migratory divide of sympatric blackcaps (Sylvia atricapilla)

The recent formation of a migratory divide in the blackcap (Sylvia atricapilla) involves sympatrically breeding birds migrating to different overwintering quarters. Within the last 50 years, a novel migratory strategy has evolved resulting in an increasing proportion of birds now wintering in Britain instead of migrating to the traditional sites in the Mediterranean area. This rapid microevolution has been attributed to allochronic spring arrival of migrants from the respective wintering quarters leading to assortative mating. Moreover, blackcaps wintering in Britain may experience fitness advantages owing to improved local wintering conditions. We used stable hydrogen isotope signatures (deltaD) to scrutinize the degree of temporal segregation of blackcaps upon spring arrival and to test for carry-over effects in body condition associated with the disparate wintering environments. Although we found that migrants from Britain arrive significantly earlier on German breeding grounds than migrants from the Mediterranean region, we also found a considerable overlap in arrival times. In a resampling model, the mean probability of assortative mating of birds wintering in Britain is </=28% in both years. These results suggest that allochrony alone is not a strong isolating barrier between the two subpopulations. Migrants from both wintering locations did not differ in terms of body mass, mass-tarsus residuals or mass-tarsus ratio and arrived in a similar reproductive disposition. Thus, blackcaps wintering in Britain do not gain an apparent fitness advantage on spring migration due to carry-over effects in body condition. Future studies should explore additional factors such as differences in song quality and habitat that might contribute to the rapid microevolution of the blackcap.

Proximate control and adaptive potential of protandrous migration in birds

Migration determines where, when, and in which order males and females converge for reproduction. Protandry, the earlier arrival of males relative to females at the site of reproduction, is a widespread phenomenon found in many migratory organisms. Detailed knowledge of the determinants of protandry is becoming increasingly important for predicting how migratory species and populations will respond to rapid phenological shifts caused by climatic change. Here, we review and discuss the potential mechanisms underlying protandrous migration in birds, focusing on evidence from passerine species. Latitudinal segregation during the non-breeding period and differences in the initiation of spring migration are probably the key determinants of protandrous arrival at the breeding sites, while sexual differences in speed of migration appear to play a minor role. Experimental evidence suggests that differences between the sexes in the onset of spring migratory activity are caused by differences in circannual rhythmicity or by photoperiodic responsiveness. Both of these mechanisms are hardwired and could prevent individuals from responding plastically to chronic changes in temperature at the breeding grounds. As a consequence, adaptive changes in both the timing of arrival in spring and of reproduction will require evolutionary (genetic) changes of the cue-response systems underlying the initiation and extent of migration in both males and females.

Wood Warbler Phylloscopus sibilatrix: a nomadic insectivore in search of safe breeding grounds?

Capsule Wood Warbler population crashes coincided with local rodent outbreaks; arriving birds did not settle when rodent densities were high, apparently perceiving such conditions as too dangerous. Aims To look for causes of Wood Warbler nomadic behaviour, and to check whether local fluctuations were due to variation in weather, food availability or perceived predation risk. Methods Using long‐term data from Białowieża National Park (eastern Poland) we checked whether variation in Wood Warbler numbers and nesting success were related to temperatures during spring arrival, availability of folivorous caterpillars or to rodent numbers. Results Neither Wood Warbler numbers, nor rates of their change were correlated with temperatures. Numbers of birds were positively correlated with the numbers of caterpillars, but nesting success during caterpillar outbreaks was not especially high. High rodent numbers coincided with low Wood Warbler numbers and strong numerical declines of Wood Warblers. The expectation of higher nest depredation during the outbreaks was only partially confirmed. Conclusion The results are consistent only with the safety hypothesis: the arriving Wood Warblers refused to settle in rodent outbreak areas. Thus, Wood Warbler nomadic behaviour could result from their attempts to find safe breeding places.

Age- and sex-dependent spring arrival dates of Eastern Kingbirds

ABSTRACT Among migratory passerines, the first birds to arrive on the breeding grounds are usually older males. Early arrival by older birds may be driven by experience, age-dependent changes in body condition, age-dependent access to resources during the nonbreeding period, or latitudinal segregation by age. Males may arrive earlier than females (protandry) because males maintain better condition due to greater access to resources during the winter, or because selection favors early arriving males that acquire the best territories or experience enhanced mating opportunities. During a 4-yr study (2004–2007) in Oregon, we found that older Eastern Kingbirds (Tyrannus tyrannus), regardless of sex, arrived nearly a week before younger birds and that males arrived about 5 d before females. Age- and sex-dependent arrival dates do not appear to be related to differences in body condition, social dominance in winter, or latitudinal segregation, and protandry is unrelated to the ability of early-arriving males to acquire high-quality territories. Instead, we propose that young birds have less to gain from early arrival because of their probable inability to displace experienced birds from prime territories and that protandry evolved due to enhanced mating opportunities for early arriving males that arise from the high rates of extra-pair matings in our population of Eastern Kingbirds. Entre los migrantes paserinos, los primeros individuos en arribar a las áreas de reproducción son usualmente los machos viejos. El arribo temprano de los individuos viejos puede estar influenciado por la experiencia, cambios en la condición corporal dependiente de la edad, acceso a recursos durante la época no reproductiva dependiente de la edad, o segregación latitudinal por edades. El arribo temprano de los machos en comparación con las hembras (protandria) existe posiblemente porque los machos mantienen una mejor condición debido a un mayor acceso a recursos durante el invierno, o puede haber evolucionado porque los machos que arriban temprano adquieren los mejores territorios o presentan incremento en oportunidades de apareamiento. Durante un estudio de cuatro años (2004–2007) en Oregon, encontramos que individuos viejos del Eastern Kingbirds (Tyrannus tyrannus), sin importar el sexo, arribaron casi una semana antes que los individuos jóvenes y que los machos arribaron al rededor de cinco días antes que las hembras. Las fechas de arribo dependientes de la edad y el sexo no parecen estar relacionados con diferencias en las condiciones corporales, dominancia social durante el invierno o segregación latitudinal y la protandria no esta relacionada con la habilidad de los machos de arribar tempranamente para adquirir territorios de alta calidad. En vez, nosotros proponemos que las aves jóvenes tienen menos que ganar con el arribo temprano debido a la probable inhabilidad de desplazar a los individuos experimentados de los habitas primarios, y que la protandria evoluciono para incrementar oportunidades de apareamiento de los machos que llegan temprano los cuales sobresalen por sus altas tasas de copula extra pareja en nuestra población de Eastern Kingbirds.

Relationship between arrival date, hatching date and breeding success of the white stork (Ciconia ciconia) in Slovakia

AbstractChanges in the spring arrival dates of migrant birds have been reported from a range of locations and many authors have focused on long-term trends and their relationship to temperature and other climatic events. Perhaps more importantly, changed arrival dates may have consequences for the breeding dates of birds which strongly influence breeding success. In this paper we take the opportunity provided by a monitoring scheme of the white stork (Ciconia ciconia) to examine several features of the timing of arrival and breeding in relation to chick production in Slovakia during the period 1978–2002. First arrival dates ranged from 5th March to 30th April, and hatching dates varied between 26th April and 8th July. Generally, early arriving pairs started breeding earlier and a shorter interval between the arrival of the first partner and breeding, expressed here as hatching date, resulted in higher breeding success.