Resident and transient dynamics, site fidelity and survival in wintering Blackcaps Sylvia atricapilla: evidence from capture–recapture analyses

In their winter quarters, migrant birds may either remain within a small area (resident strategy) or move frequently over a large area looking for locally abundant food (transient strategy). It has been suggested that both strategies could simultaneously occur in the same population. We used time-since-marking capture–recapture models to infer the coexistence of these two behavioural strategies (transient and resident) among wintering Blackcaps Sylvia atricapilla using weekly recapture data over a 7-year period. A related question is whether Blackcaps, if surviving to the next winter, always return to the same wintering area, so we also used this approach to analyse winter site fidelity and to estimate annual survival probabilities. Model selection supported the existence of heterogeneity in survival estimates for both the within-season and the interannual survival probabilities, i.e. there was evidence for the existence of transients. It was estimated that 26% of the Blackcaps were resident during the winter. Mean apparent annual survival probability was 0.46 (se = ±0.11). However, there was some evidence suggesting that not all individuals showed winter site fidelity. The estimated proportion of individuals that, if alive, returned to the wintering area was 28%. This is the first study to show the existence of these two behavioural strategies (residence and transience) among wintering Blackcaps, and the first confirming this pattern using capture–recapture models. These models considering transient and resident dynamics may become an important tool with which to analyse wintering strategies.     

Mark-resight estimates of seasonal variation in harbor seal abundance and site fidelity

Monitoring trends in abundance of pinnipeds typically involves counting seals at terrestrial haul-out sites during the breeding season. Counts of seals made at other times of the year are typically lower; however, it is often unknown whether this is because fewer animals are present or whether lower counts simply reflect a reduction in haul-out probability. Here we illustrate how photo-identification data from an individual-based study of harbor seals (Phoca vitulina) can be used to estimate seasonal variation in abundance and site fidelity. Monthly data collected over a two-year period were analyzed using a mark-recapture mark-resight model accounting for individuals transitioning between observable and unobservable states. Levels of site fidelity were high throughout the year and abundance estimates showed no seasonal pattern. This suggests that individual seals used haul-out sites to the same extent throughout the year, and that peaks in counts during the breeding season are a result of seasonal changes in haul-out probability. The results of this study have implications for understanding population sub-structuring, gene flow and disease spread.     

How do Robins Erithacus rubecula resident in Iberia respond to seasonal flooding by conspecific migrants?

Capsule?The majority of Robins in Iberia are sedentary and stay in their nesting areas despite the presumed increased competition that results from the seasonal flooding of the area by conspecific migrants.

Aims?To evaluate if Robins in Iberia are displaced from their nesting areas by the presence of large numbers of competitors originating from higher latitudes.

Methods?Data from constant effort ringing sites were used to estimate the proportion of Robins that are strictly sedentary and the seasonal variation in Robin numbers. Hydrogen stable isotope ratios (δ²H) in feathers, and sex ratios determined through molecular techniques, allowed an insight into the numerical importance of invading Robins from higher latitudes.

Results?Robins were more numerous outside the breeding season, with clear influxes in autumn. Around half of the locally nesting Robins were captured during winter, indicating they are truly sedentary. δ²H in feathers suggests that a wide mixture of Robins from all European latitudes were present in winter, and these data, together with sex ratios, suggest that there may be similar numbers of local and foreign individuals in winter at the main study site.

Conclusion?Despite the occupation of their range by migrants, local birds are largely sedentary.     

Seasonal Survival Probabilities Suggest Low Migration Mortality in Migrating Bats

Migration is adaptive if survival benefits are larger than costs of residency. Many aspects of bat migration ecology such as migratory costs, stopover site use and fidelity are largely unknown. Since many migrating bats are endangered, such information is urgently needed to promote conservation. We selected the migrating Leisler''s bat (Nyctalus leisleri) as model species and collected capture-recapture data in southern Switzerland year round during 6 years. We estimated seasonal survival and site fidelity with Cormack-Jolly-Seber models that accounted for the presence of transients fitted with Bayesian methods and assessed differences between sexes and seasons. Activity peaked in autumn and spring, whereas very few individuals were caught during summer. We hypothesize that the study site is a migratory stopover site used during fall and spring migration for most individuals, but there is also evidence for wintering. Additionally, we found strong clues for mating during fall. Summer survival that included two major migratory journeys was identical to winter survival in males and slightly higher in females, suggesting that the migratory journeys did not bear significant costs in terms of survival. Transience probability was in both seasons higher in males than in females. Our results suggest that, similarly to birds, Leisler''s bat also use stopover sites during migration with high site fidelity. In contrast to most birds, the stopover site was also used for mating and migratory costs in terms of survival seemed to be low. Transients'' analyses highlighted strong individual variation in site use which makes particularly challenging the study and modelling of their populations as well as their conservation.     

Home-ranges and patterns of spatial use in territorial Bonelli's Eagles Aquila fasciata

Bonelli's Eagle Aquila fasciata is one of the rarest birds of prey in Europe, where it has suffered a significant decline in recent decades. We present information on the home-ranges and spatial parameters of 18 Bonelli's Eagles radiotracked in 2002–2006 in Catalonia (northeast Spain) and describe the home-range probability kernel, distances moved, breeding area eccentricity, territorial overlap, nearest neighbour distance and breeding site fidelity, and assess the influence of sex, breeding status, season and geographical area on these parameters. Median home-range according to the minimum convex polygon (MCP) and 95% kernel were 50.3 and 36.1 km², respectively. The median breeding area eccentricity was 1477 m. There was considerable overlap in the home-range of both sexes within pairs (MCP: 71.4% and 95% kernel: 98.5%), indicating close pair bonding and similar foraging patterns. Overlap in home-ranges of up to 15% between neighbouring individuals also occurred and was positively related to breeding pair density. There was no difference in spatial parameters between sexes or with breeding status, but during the non-breeding season Eagles had larger home-ranges and stayed further from nests. The high consistency across birds suggests a pattern of spatial use that is characteristic of this species. The high level of use of breeding areas and their surroundings (50% kernel) throughout the year makes it important that these areas be protected from human disturbance. Additionally, it is necessary that heavily used areas away from nesting sites, which are used for foraging and roosting, are identified, protected and managed in a sustainable fashion.     

Site fidelity,residency, and abundance of bottlenose dolphins (Tursiops sp.) in Adelaide's coastal waters,South Australia

Little is known about the ecology and behavior of southern Australian bottlenose dolphins (Tursiops sp.). This hinders assessment of their conservation status and informed decision‐making concerning their management. We used boat‐based surveys and photo‐identification data to investigate site fidelity, residency patterns, and the abundance of southern Australian bottlenose dolphins in Adelaide's coastal waters. Sighting rates and site fidelity varied amongst individuals, and agglomerative hierarchical cluster analysis led to the categorization of individuals into one of three groups: occasional visitors, seasonal residents, or year‐round residents. Lagged identification rates indicated that these dolphins used the study area regularly from year to year following a model of emigration and reimmigration. Abundance estimates obtained from multisample closed capture‐recapture models ranged from 95 individuals (SE ± 45.20) in winter 2013 to 239 (SE ± 54.91) in summer 2014. The varying levels of site fidelity and residency, and the relatively high number of dolphins found throughout the study area highlights the Adelaide metropolitan coast as an important habitat for bottlenose dolphins. As these dolphins also appear to spend considerable time outside the study area, future research, conservation, and management efforts on this population must take into account anthropogenic activities within Adelaide's coastal waters and their adjacencies.     

The cost of migratory prey: seasonal changes in semi‐domestic reindeer distribution influences breeding success of Eurasian lynx in northern Norway

Migratory prey is a widespread phenomenon that has implications for predator–prey interactions. By creating large temporal variation in resource availability between seasons it becomes challenging for carnivores to secure a regular year‐round supply of food. Some predators may respond by following their migratory prey, however, most predators are sedentary and experience strong seasonal variation in resource availability. Increased predation on alternative prey may dampen such seasonal resource fluctuations, but reduced reproduction rates in predators is a predicted consequence of migratory primary prey behavior that has received little empirical attention. We used data from 23 GPS collared Eurasian lynx Lynx lynx monitored during 2007–2013 in northern Norway, to examine how spatio‐temporal variation in the migratory behavior of semi‐domestic reindeer Rangifer tarandus influences lynx spatial organization and reproductive success using estimates of seasonal home range overlap and breeding success. We found that lynx of both sexes maintained seasonally stable home ranges and exhibited site fidelity across years, independent of whether they had access to reindeer throughout the year or experienced a scarcity of reindeer in winter due to migration. However, lynx without access to reindeer in winter showed a decreased probability of reproducing and a tendency for lowered kitten survival into their first winter, when compared to female lynx with reindeer available year around. This supports the hypothesis that sedentary predators experience demographic costs in systems with migratory primary prey. Changes in the migratory behavior of ungulates, including disrupted migrations, is therefore likely to have bottom–up effects on the population dynamics of sedentary predators as well as the previously documented consequences for ungulate population dynamics.     

Variable individual consistency in timing and destination of winter migrating fish

Migration is an important event in the life history of many animals, but there is considerable variation within populations in the timing and final destination. Such differential migration at the population level can be strongly determined by individuals showing different consistencies in migratory traits. By tagging individual cyprinid fish with uniquely coded electronic tags, and recording their winter migrations from lakes to streams for 6 consecutive years, we obtained highly detailed long-term information on the differential migration patterns of individuals. We found that individual migrants showed consistent site fidelities for over-wintering streams over multiple migratory seasons and that they were also consistent in their seasonal timing of migration. Our data also suggest that consistency itself can be considered as an individual trait, with migrants that exhibit consistent site fidelity also showing consistency in migratory timing. The finding of a mixture of both consistent and inconsistent individuals within a population furthers our understanding of intrapopulation variability in migration strategies, and we hypothesize that environmental variation can maintain such different strategies.     

Perceived wintering latitude determines timing of song output in a migratory bird

Migratory bird populations frequently consist of individuals that overwinter variable distances from the breeding site. Seasonal changes in photoperiod, which varies with latitude, underlie seasonal changes in singing frequency in birds. Therefore, migratory populations that consist of individuals that overwinter at different latitudes with large overwintering ranges could experience within‐population variation in seasonal production of song. To test the influence of overwintering latitude on intrapopulation variance in song production in the spring, we subjected two groups of Eastern Song Sparrows (Melospiza melodia melodia) from the same partially migratory breeding population to different photoperiodic schedules associated with a 1,300‐km difference in overwintering location. One group remained on the natural photoperiodic schedule of the breeding site (resident group) while the other group experienced a nonbreeding photoperiod that mimicked a southern migration in the fall followed by a northern migration back to the breeding site in the spring (migratory group). We compared song output between the two groups in three different stages (nonbreeding, prebreeding, and breeding). Little singing occurred during nonbreeding stage sample dates (20 November, 6 December) for the resident group, and no singing occurred for the migrant group. During the prebreeding stage (27 January, 7 February), significantly more singing occurred in the resident group than in the migrant group. During the breeding stage (21 March, 4 April), after a simulated migration for the migrants, song output was similar in both groups. These results suggest that within‐population variation in wintering latitude may contribute to variation in seasonal changes in singing behavior, which may covary with readiness to breed. Studies utilizing confirmed migrants and residents, rather than merely simulated migrants and residents, are also needed to better understand these processes.     

Landscape movements of migratory birds and bats reveal an expanded scale of stopover

Many species of birds and bats undertake seasonal migrations between breeding and over-wintering sites. En-route, migrants alternate periods of flight with time spent at stopover--the time and space where individuals rest and refuel for subsequent flights. We assessed the spatial scale of movements made by migrants during stopover by using an array of automated telemetry receivers with multiple antennae to track the daily location of individuals over a geographic area ~20 × 40 km. We tracked the movements of 322 individuals of seven migratory vertebrate species (5 passerines, 1 owl and 1 bat) during spring and fall migratory stopover on and adjacent to a large lake peninsula. Our results show that many individuals leaving their capture site relocate within the same landscape at some point during stopover, moving as much as 30 km distant from their site of initial capture. We show that many apparent nocturnal departures from stopover sites are not a resumption of migration in the strictest sense, but are instead relocations that represent continued stopover at a broader spatial scale.     

Abundance, species richness and energy availability in the North American avifauna

Aim To determine how species richness, abundance, biomass, energy use and mean number of individuals per species scale with environmental energy availability in wintering and breeding avian assemblages, and to contrast assemblages of (i) common and rare species and (ii) breeding residents and migrants. To assess whether such patterns are compatible with the ‘more individuals hypothesis’ (MIH) that high‐energy areas are species‐rich because they support larger populations that are buffered against extinction. Location The North American continent (latitudinal range 23.4 °?48.1 °N; longitudinal range 124.2°?68.7° W). Methods Avian species richness, abundance, biomass and energy use were calculated for 295 Resident Bird Count plots. Environmental energy availability was measured using ambient temperature and the Normalized Difference Vegetation Index (NDVI), a close correlate of plant productivity. Analyses took plot area into account, and were conducted (with and without taking habitat type into account) using general linear models and spatial mixed models. Results Positive species–energy relationships were exhibited by both wintering and breeding assemblages, but were stronger in the former. The structure of winter assemblages responded more strongly to temperature than NDVI, while breeding assemblages tended to respond more strongly to NDVI. Breeding residents responded to annual measures of energy availability while breeding migrants and the winter assemblage responded more strongly to seasonal measures. In the winter assemblage, rare and common species exhibited species–energy relationships of a similar strength, but common breeding species exhibited a much stronger relationship than rare breeding species. In both breeding and wintering assemblages, abundance, biomass and energy use increased with energy availability and species richness. Energy availability was a poor predictor of the mean number of individuals per species. Main conclusions The nature of the species–energy relationship varies seasonally and with the manner in which energy availability is measured. Our data suggest that residents are less able to respond to seasonal fluxes in resource availability than long‐distance migrants. Increasing species richness and energy availability is associated with increasing numbers of individuals, biomass and energy use. While these observations are compatible with the MIH our data provide only equivocal support for this hypothesis, as the rarest species do not exhibit the strongest species–energy relationships.     

Patterns of territory settlement and consequences for breeding success in the Northern Wheatear Oenanthe oenanthe

We examined the pattern of territory settlement and its consequences for breeding success in the Northern Wheatear Oenanthe oenanthe on Bardsey Island, Wales, during the breeding seasons of 1991-93. Males returned earlier than females, and older males returned earlier than first-year breeders. Although their boundaries shifted between years, the general location of territories was consistent during the three-year study. There was a high degree of fidelity to area and territory between years for both sexes. The order of territory settlement, from which a territory rank was calculated, was highly consistent for males between years irrespective of individual settlement patterns and territory fidelity. Patterns of territory settlement were less predictable for females, although there was a significant correlation between the mean territory ranks of paired males and females. There was a male-biased sex ratio in each year, and between 5% and 26% of males remained unpaired throughout the breeding season. Male mating status and breeding success were dependent on arrival date, territory rank and breeding density. Early-arriving, usually older, males were able to settle on territories first and were more likely to pair, while later-arriving individuals were more likely to remain unmated. These effects were consistent between years, and consequently territories could be classified as either preferred (accounting for proportionately more breeding attempts) or non-preferred. Territory quality as opposed to individual quality appeared to explain much of the variation in breeding success, and both sexes benefited by breeding on preferred territories through enhanced breeding success and an increased probability that their offspring would be recruited to the population.     

Kin-related social organization in a winter population of the voleClethrionomys rufocanus

Kinship amongClethrionomys rufocanus was investigated during the winter of 1992/93 in a 3-ha enclosure using both molecular and catch-mark-release techniques. Forty-six adult voles (22 males and 24 females) having high heterozygosities, which were collected from several natural populations, were released into the enclosure on 29 September 1992. Most fall-born individuals of both sexes stayed in their natal site during the non-breeding period (December–March), although reproductively active females dispersed during the fall breeding season (October–November). These philopatric individuals aggregated and formed an maternal family in the winter. Several females which failed to reproduce were solitary during this season. Some individuals which were derived from several families also aggregated into a mixed lineage group. Survival rate of fall-born voles from earlier litters was higher than that from later ones. Maternal families broke up soon after the onset of spring reproduction. Most females established a territory near the wintering site and made a kincluster, in which close relatives neighbored each other. Maternal families in winter bring about female kin-clusters in spring, which may influence reproductive output in the breeding season.     

Rapid 'evolution' of migratory behaviour in the introduced house finch of eastern North America

The house finch (Carpodacus mexicanus) of eastern North America was introduced onto Long Island, New York, around 1940. The source is presumed to be southern California, where ca. 80% of individuals are completely sedentary. The eastern population has become migratory: by the early 1960s, 36% of eastern house finches were performing migratory movements (more than 80 km from their banding site) and that proportion has fluctuated between 28% and 54% in succeeding years. The movements of birds banded during the breeding season and recovered in winter were strongly orientated toward the south-west, and the same pattern was evident in the earliest recoveries (1958 to 1966); recoveries of birds banded during winter and recovered in the breeding season were orientated toward the north-east. The average distance of migration has continued to increase logarithmically. Areas colonized later, as the range expanded, were characterized by initial long migration distances and high proportions of migrants, suggesting that these traits have evolved in the eastern population. Eastern house finches are partial migrants: not all individuals migrate, and birds that migrate some winters remain in breeding areas in others. Younger birds exhibit a stronger tendency to migrate. A very few western (including southern California) house finches moved long distances, but they did so in directions consistent with seasonal migration, indicating that the machinery subserving migratory behaviour pre-existed in the parent population.     

High foraging site fidelity and spatial segregation among individual great black‐backed gulls

Individual foraging site fidelity, whereby individuals repeatedly visit the same foraging areas, is widespread in nature, and likely benefits individuals through higher foraging efficiency and potentially, higher breeding success. It may arise as a consequence of habitat or resource specialisation, or alternatively, where resources are abundant or predictable, the partitioning of space might guarantee individuals exclusive foraging opportunities. We tracked seven adult great black‐backed gulls Larus marinus at a North Sea colony from early incubation to the end of the breeding season in 2016, providing a total of 1170 foraging trips over a mean ± SD tracking period of 67 ± 16 days. There was clear spatial segregation between individuals, with almost no overlap of their core areas (50% utilisation distribution) during incubation and chick‐rearing. Core areas were relatively small and there was high repeatability (R ± SE) in foraging parameters, including initial departure direction (0.73 ± 0.11), foraging range (0.41 ± 0.14) and cumulative distance travelled (0.19 ± 0.1) throughout the breeding season. Despite the low spatial overlap, there was little evidence of differential habitat use by individuals. The near‐exclusive individual foraging areas of this species, usually considered to be a generalist, indicate that where there is high resource availability throughout the breeding season and a small local population, individuals appear to adopt a territorial strategy which likely reduces intraspecific competition.     

Characterizing dispersal patterns in a threatened seabird with limited genetic structure

Genetic assignment methods provide an appealing approach for characterizing dispersal patterns on ecological time scales, but require sufficient genetic differentiation to accurately identify migrants and a large enough sample size of migrants to, for example, compare dispersal between sexes or age classes. We demonstrate that assignment methods can be rigorously used to characterize dispersal patterns in a marbled murrelet (Brachyramphus marmoratus) population from central California that numbers approximately 600 individuals and is only moderately differentiated (F_ST～ 0.03) from larger populations to the north. We used coalescent simulations to select a significance level that resulted in a low and approximately equal expected number of type I and II errors and then used this significance level to identify a population of origin for 589 individuals genotyped at 13 microsatellite loci. The proportion of migrants in central California was greatest during winter when 83% of individuals were classified as migrants compared to lower proportions during the breeding (6%) and post‐breeding (8%) seasons. Dispersal was also biased toward young and female individuals, as is typical in birds. Migrants were rarely members of parent‐offspring pairs, suggesting that they contributed few young to the central California population. A greater number of migrants than expected under equilibrium conditions, a lack of individuals with mixed ancestry, and a small number of potential source populations (two), likely allowed us to use assignment methods to rigorously characterize dispersal patterns for a population that was larger and less differentiated than typically thought required for the identification of migrants.     

ON THE BIRDS OF MOROCCO

Fifteen months were spent in Morocco. A few ecological aspects of the country are described, together with their influence on the dispersal of birds in winter. Some winter visitors are listed and discussed, several species were much commoner in the winter of 1962/63 than in 1963/64, in some cases presumably as a result of the cold weather in Europe, although in others not obviously so. Cold-weather movements of gulls, Lapwings and Cranes were observed. Individuals of species that are normally trans-Saharan migrants winter in Morocco in small numbers. Spring migration in southeast Morocco is excluded from discussion, but autumn migration in western Morocco is summarized and compared with existing data. The systematic list is devoted largely to winter visitors and passage migrants, but resident species are listed when new localities, breeding data or field notes warrant their inclusion. Six species not hitherto recorded in Morocco, were seen.     

Home sweet home: evidence for nest‐fidelity in the rocky intertidal fish,the shanny Lipophrys pholis

The ability to be faithful to a particular area or site was analysed in the shanny Lipophrys pholis. Using passive integrated transponders, adults from a population of L. pholis at Cabo Raso, Portugal, were followed over a period of 3 years. The findings showed that site fidelity is a consistent behaviour during the breeding season with specific breeding males being found only in particular sectors within the area, and in specific nests throughout the years. The fact that, in general, L. pholis individuals were absent from the study area during the non‐breeding season and breeding males were recorded returning to the same nests and sectors for consecutive breeding seasons suggests that they have developed excellent homing abilities. Translocation data corroborate this idea showing that breeding males successfully returned to their nests after a displacement of >100 m. Altogether, these findings highlight the relevance of life‐history traits (e.g. nesting) in the conditioning of site fidelity and homing for this species of rocky intertidal fish, and more importantly, provide evidence for the need of a well‐developed navigational system.     

Prospectors' colony attendance is sex-specific and increases future recruitment chances in a seabird

In most long-lived vertebrates, including seabirds, young non-breeders often attend potential breeding sites. In seabird colonies, this prospecting behaviour has nearly never been studied with respect to potential sex-specific benefits, and its fitness consequences are largely unknown. We compared attendance patterns of sexed common tern prospectors at six subcolonies with future breeding status and nesting site choice. We also tested for potential effects of population density. Birds that arrived earlier at the colony were recorded more often along the season. This arrival effect was stronger in males, which generally spent more time at the colony. Birds prospecting for two consecutive years attended the colony more intensively in the second year. A high colony attendance enhanced recruitment probability in both sexes, but only in females, it was linked with a higher probability to return. Attendance at a preferred subcolony increased during the season. For first breeding, individuals favoured the subcolony where they had prospected most intensively in the previous season. In males, this subcolony fidelity was stronger and increased simultaneously to breeding pair density. We conclude that prospecting is a process of integration into the community of breeders, and that benefits are higher for males, the more territorial sex in this species.     

内蒙古乌海市鸟类区系特征及群落结构

2009年4月至2010年3月对内蒙古乌海市的鸟类区系及群落结构进行了调查研究。共记录到鸟类132种,隶属于17目37科。其中留鸟26种,夏候鸟71种,旅鸟27种,冬候鸟8种。繁殖鸟有97种,其中古北界鸟类有83种,占繁殖鸟类种数的85.6%。研究发现不同季节、不同生境中的鸟类群落特征差异较大。春季的鸟类多样性指数和均匀度指数均最高;湿地的鸟类多样性指数最高。本文基于研究结果提出了对乌海市鸟类及其生存环境的保护建议。