Sexual segregation in winter, spring dispersal and habitat use in the pheasant (Phasianus colchicus)

Sexual segregation, spring dispersal and late winter to spring habitat selection were studied in the pheasant Phasianus colchicus L. on two areas for which the proportions of different habitats were similar. On one of the sites (Damerham) hand-reared pheasants were released for shooting. On the other (Fulwell) no releasing or shooting took place.
The sex ratio of birds feeding in fields in autumn favoured males because females fed in groups within woods. Groups of birds were significantly segregated by sex during early to late winter periods, but by late March they were not. Male groups and solitary males in winter were more evenly dispersed than female groups.
At Fulwell, female winter groups consisted of regular group members (mainly adults) and transitory individuals called 'drifters' (mainly immatures).
Females in their first breeding attempt dispersed further from their winter range to their breeding range than did adult females and females dispersed further than males. Males gaining a territory for the first time moved significantly further than old territory owners. Territorial males moved less than non-territorial males between successive spring ranges.
During March June, habitat use by 33 radio-tagged females changed markedly from mixed and deciduous woodland to fields sown with winter and spring corn. The implications for management are outlined.     

Territory acquisition during winter by juvenile Willow Tits Parus montanus

Willow Tits Parus montanus live within exclusive territories in non-kin winter flocks with a dominance hierarchy in which males dominate females and adults dominate juveniles. Because they live in habitats that are saturated with dominant territory owners, the options of subordinate juveniles surviving the winter are: (1) to become a dominant owner of a vacated territory, (2) to stay in an occupied territory and hope for ownership or (3) to leave the area and hope for territory acquisition elsewhere. Removal experiments during December to February revealed that particularly the most dominant of the juvenile pairs left their own flock territory and replaced birds experimentally removed from a neighbouring flock, if by doing so they increased their own dominance position. It is suggested that juvenile Willow Tits updated their information about the composition and dominance structure of adjacent winter flocks by regularly visiting these territories and attempted to become dominant owners during winter, thereby increasing their chances of breeding.     

Foraging movements of emperor penguins at Pointe Géologie, Antarctica

The foraging distributions of 20 breeding emperor penguins were investigated at Pointe Géologie, Terre Adélie, Antarctica by using satellite telemetry in 2005 and 2006 during early and late winter, as well as during late spring and summer, corresponding to incubation, early chick-brooding, late chick-rearing and the adult pre-moult period, respectively. Dive depth records of three post-egg-laying females, two post-incubating males and four late chick-rearing adults were examined, as well as the horizontal space use by these birds. Foraging ranges of chick-provisioning penguins extended over the Antarctic shelf and were constricted by winter pack-ice. During spring ice break-up, the foraging ranges rarely exceeded the shelf slope, although seawater access was apparently almost unlimited. Winter females appeared constrained in their access to open water but used fissures in the sea ice and expanded their prey search effort by expanding the horizontal search component underwater. Birds in spring however, showed higher area-restricted-search than did birds in winter. Despite different seasonal foraging strategies, chick-rearing penguins exploited similar areas as indicated by both a high ‘Area-Restricted-Search Index’ and high ‘Catch Per Unit Effort’. During pre-moult trips, emperor penguins ranged much farther offshore than breeding birds, which argues for particularly profitable oceanic feeding areas which can be exploited when the time constraints imposed by having to return to a central place to provision the chick no longer apply.     

Family-based winter territoriality in western bluebirds, Sialia mexicana: the structure and dynamics of winter groups

Winter residency is characteristic of the majority of cooperatively breeding birds, but the composition and dynamics of winter groups have been examined in relatively few. In 1996-1998, we examined winter territoriality in the western bluebird, a year-round resident that shows a limited degree of helping behaviour in central coastal California, U.S.A. In spring, most western bluebirds breed as socially monogamous pairs, but a small proportion of pairs (3-16%) have additional breeding-age males helping at the nest, usually assisting parents or brothers. We found that year-round residents commonly wintered in family groups that defended territories similar to those used in spring. Winter groups had an even sex ratio and formed early in the autumn, when hatch-year birds dispersed. More females than males left their natal groups to be replaced by an influx of immigrant hatch-year birds. Winter groups typically consisted of breeders and one or two sons from the prior breeding season along with one or more immigrant females. A second period of dispersal occurred in spring when winter groups broke up and most birds other than the breeding pair left the winter territory. When they bred, yearling males and females often bred with unrelated individuals from their winter groups. Sons were more likely to remain on the study area as yearlings when they wintered with both parents than when they wintered with just one parent. We suggest that young males stay the winter due to benefits of remaining in family groups on mistletoe-based winter territories. Subsequent localized dispersal of sons then leads to opportunistic kin-based interactions later in life. Copyright 2001 The Association for the Study of Animal Behaviour.     

Social class,socially-induced loss,recruitment and breeding of red grouse

Summary Individually marked red grouse (Lagopus lagopus scoticus) could be distinguished as territorial or non-territorial from November till the next spring. Territorial birds survived well and many reared young, but numerous nonterritorial birds died or disappeared, and none paired up or reared young. Differences in spring sex ratio between years had already been set in the previous autumn's territorial stock. Many old birds which had been territorial in earlier seasons lost territories after an annual re-distribution of territory each October–November. Thereafter very few of them were seen alive on the area over the winter, and many were found dead, whereas nearly all old birds that kept their territories were still there in spring. The number of birds in spring and the fate of individuals over winter were predicted reasonably accurately from observations of behaviour in the previous November–December. Thus, differences of social class in autumn were critical to a bird's survival to breed in the next summer and to its chances of contesting for territory and breeding in subsequent years.     

Body condition, territory ownership and age-related reproductive performance in Spruce Grouse Dendragapus canadensis hens

Adult Spruce Grouse Dendragapus canadensis hens show better reproductive performance (i.e. larger clutch size, earlier clutch initiation, higher frequency of renesting) than year-lings. Body and breast muscle weights, condition indices and relative body composition were compared between adult and yearling birds from northeastern Ontario, Canada, to determine whether differences in endogenous reserves mobilized for egg production and (or) territory ownership could explain these differences in reproductive performance. Adults and yearlings showed similar declines in body-weight, breast muscle weight and condition indices from the pre-laying to the post-laying period, but no significant interage differences emerged at any stage of the breeding season. Changes in body composition, especially gut structure, were similar in all birds; this result is consistent with a dietary shift in both age classes from a fibrous winter diet to more succulent foods in spring. Non-territory-holding (replacement) yearlings also had similar body-weights and breast muscle weights and were in similar condition to territory holders (residents) in the pre-laying period. My findings do not support the hypothesis that differences in body condition and territory occupancy can account for differences in age-related reproductive performance in Spruce Grouse.     

Spatial distribution and settlement strategies in willow ptarmigan

In heterogeneous landscapes individuals select among several habitat patches. The fitness rewards of these choices are assumed to play an important role in the distribution of individuals across landscapes. Individuals can either use environmental cues to directly assess the quality of breeding sites, or rely on social cues to guide the settlement decision. We estimated the density of adult birds and per capita reproductive success of willow ptarmigan over 5–15 years in 42 survey areas, nested within 5 spatially separated populations in south-central Norway. Our aims were to (1) examine spatial and temporal patterns of variation in densities of adult birds (i.e., the breeding densities) and reproductive success (juveniles/pair) measured in autumn and (2) evaluate which habitat distribution model best described the distribution of willow ptarmigan across heterogeneous mountain landscapes. Variation in density of adult birds was primarily attributable to variation between survey areas which could arise from spatial heterogeneity in adult survival or as a consequence of spacing behavior of juveniles during the settlement stage. In contrast, reproductive success was more variable between years and did not vary consistently between survey areas once year effects were accounted for. The lack of any relationship between the density of adult birds and reproductive success supported the predictions of an ideal free distribution (IFD), implying that within years, the mean reproductive success was approximately equal across survey areas. However, analysis based on Taylor's power law (i.e., the relationship between logarithms of spatial variance and mean density of adult birds) suggested that aggregation was stronger than expected under IFD. This implies that the relative change in density of adult birds was larger in areas with high mean densities than in areas with low densities. The exact mechanisms causing this statistical pattern are unclear, but based on the breeding biology of willow ptarmigan we suggest that yearlings are attracted to areas of high densities during the settlement period in spring. Our study was conducted during a period of low overall density and we suggest that this pattern might be particular to such situations. This implies that the presence of conspecifics might represent a cue signaling high adult survival and thus high habitat quality.     

Density changes and habitat shift of great grey shrike <Emphasis Type="Italic">Lanius excubitor</Emphasis> during the non-breeding season

Bird population density and their behaviour during non-breeding periods are determined mainly by meteorological conditions which force birds to use alternative strategies — migration to areas with more advantageous conditions or adaptation to existing conditions. During the 2002/03–2004/5 non-breeding seasons in the open habitats of the Kotlina Orawsko-Nowotarska valley (S Poland) studies on population dynamics, behaviour and habitat use of great grey shrike were conducted. Results were grouped into four meteorological periods (autumn, early winter, winter and early spring). Density changes were seen between subsequent seasons (from 0.34 to 1.9 ind./10 km), as well as between meteorological periods (from 0.48 to 2.70 ind./10 km). Perching was the most frequently observed behaviour. The foraging habitats used changed in frequency. In subsequent meteorological periods a decrease of open habitats used was noted with a simultaneous increase in afforestations used. These changes did not depend on lasting snow cover. Changes in vegetation type used during hunting were not observed. Great grey shrikes most frequently used natural perches (trees, shrubs and high vegetation).     

Winter territory prospecting is associated with life‐history stage but not activity in a passerine

Finding a high quality territory is essential for many animals to reproduce successfully. Despite its importance for fitness, we know little about the process of territory prospecting in wild birds, and whether individual traits and behaviours, such as personality, co‐vary with territory prospecting. Here, we use long‐term data from a wild, insular house sparrow Passer domesticus population to test three hypotheses about territory fidelity and prospecting: 1) house sparrows show high territory fidelity between years and also during winter. 2) Individuals will prospect for a breeding territory during their first winter whereas older, more experienced individuals will keep a territory from previous years and will, therefore, show no or reduced winter territory prospecting. 3) More active behavioural types will prospect more than less active behavioural types. We use data from four winters from automatically, daily recorded nest‐box visits of 188 birds of known age. The number of nest‐boxes that each individual visited within each winter was used as a proxy of winter territory prospecting. We show that house sparrows visit multiple nest‐boxes during their first winter, whereas older individuals keep territories year‐round and, potentially because of this, indeed show reduced winter territory prospecting. Activity was not associated with the number of nest‐boxes visited. Further research is needed to investigate whether time of territory and mate acquisition differs among individuals and the possible effect on lifetime fitness.     

Effects of post-breeding moult and energetic condition on timing of songbird migration into the tropics

Each autumn billions of songbirds migrate between the temperate zone and tropics, but little is known about how events on the breeding grounds affect migration to the tropics. Here, we use light level geolocators to track the autumn migration of wood thrushes Hylocichla mustelina and test for the first time if late moult and poor physiological condition prior to migration delays arrival on the winter territory. Late nesting thrushes postponed feather moult, and birds with less advanced moult in August were significantly farther north on 10 October while en route to the tropics. Individuals in relatively poor energetic condition in August (high β-Hydroxybutyrate, low triglyceride, narrow feather growth bars) passed into the tropics significantly later in October. However, late moult and poor pre-migratory condition did not result in late arrival on the winter territory because stopover duration was highly variable late in migration. Although carry-over effects from the winter territory to spring migration may be strong in migratory songbirds, our study suggests that high reproductive effort late in the season does not impose time constraints that delay winter territory acquisition.     

Influence of Density and Climate on Population Dynamics of a Large Herbivore Under Harsh Environmental Conditions

ABSTRACT Dynamics of herbivore populations can be influenced both by density-dependent processes and climate. We used age-at-harvest data for adult female white-tailed deer (Odocoileus virginianus) collected over 23 years to estimate survival and reproduction by age class and to identify effects of environmental factors. The study population was located on Anticosti Island (QC, Canada), at the northern limit of the species' range; the population was at high density, and the landscape had scarce forage and abundant snow during winter. Despite severe environmental conditions, population growth apparently increased during the study; adult survival was similar to other populations, although reproduction appeared lower. Winter severity was not related to survival, but density affected adult female survival. Density at estrus was the main factor influencing reproduction of 2- and 3–4-year-olds and also affected reproduction of prime-aged females (5–9-yr-olds), but not of older females. Reproductive rate of younger females was influenced by environmental conditions in autumn, such as high density or snow conditions that limited forage availability. Reproductive success of 5–9- and ≥10-year-old females appeared dependent on spring conditions favoring high-quality forage, probably through effects on neonatal survival. Relative to other studies on northern ungulates, demographic processes in our study appeared to be more affected by autumn and spring climate, in addition to population density, than by winter climate. We thus propose that population density, as well as autumn and spring climate, should be considered in management strategies. Harvest data offered a unique opportunity to study forest ungulates, for which individual monitoring is rarely possible.     

Over-wintering strategies of the Lesser Sheathbill Chionis minor in an impoverished and insular environment

Summary The Lesser Sheathbill Chionis minor is an opportunistic predator and scavenger that breeds on sub-Antarctic islands during the summer season, when many other seabirds are present, especially penguins on which it is kleptoparasitic. It is a poor flyer and over-winters on its breeding grounds, where it faces a diminished food supply and low temperatures. Its foraging behaviour was suspected to be plastic enough to respond to such a variable environment, and we show how this species enlarged its niche to survive in winter. Population movements, dietary changes and monthly weight gains were quantified during a 13-month period of observation. Mortality rates, calculated over a 19-year period of banding, appeared to be age dependent: they decrease, due to competition, from juveniles to subadults, adult non-breeders, and breeders. One of the survival strategies described here is, to our knowledge, unique among birds. After the Crested Penguin colonies have been deserted, some adult sheathbills (mainly females) remained territorial, extending their territory size and diet while their partners moved to previously undefended zones in King Penguin colonies (permanent and large in the Crozet archipelago), where they competed for a winter territory and subsequently associated with another mate. After this winter mating, mobile sheathbills returned the following summer to their breeding territory and previous mate.     

GENETIC VARIATION AND TERRITORIALITY IN WILLOW PTARMIGAN (LAGOPUS LAGOPUS LAGOPUS)

We examined eight polymorphic esterase loci in 526 juvenile and adult willow ptarmigan (Lagopus lagopus lagopus) collected during autumn and spring over five years. The genetic structure of territorial birds during spring differed from birds on the study area in autumn. This can not be explained by selective winter mortality since juvenile birds in the autumn had the same genetic structure as the adults who had lived through at least one winter. In the spring, birds with intermediate heterozygosity had the largest territories and were more frequently mated than expected from random mating among autumn birds. The results suggest selective access to territories by genotype and stabilizing selection, especially among males, since natural selection is assumed to favor large territories and reproduction. Our data also suggest that the spring population consisted of both territorial and non-territorial birds. The genetic relationship between birds of established pairs in spring was lower than that between randomly drawn birds on the study area in the autumn. This together with the finding that parents with an intermediate level of genetic relationship produced the largest broods, suggest that optimal rather than maximal outbreeding is the most successful breeding strategy in this species.     

Climate change may account for the decline in British ring ouzels Turdus torquatus

1. Climate change is already affecting biodiversity, but the number of species for which reliable models relate weather and climate to demographic parameters is low. 2. We modelled the effect of temperature and rainfall on the breeding success and territory occupancy of ring ouzels Turdus torquatus (L.) in northern Britain, using data from a range of study areas, including one where there was a long-term decline in ring ouzel abundance. 3. Timing of breeding was significantly related to meteorological variables affecting birds in the early spring, though there was no evidence that laying dates had advanced. Breeding success was not significantly related to weather variables; instead, over 90% of annual variation in this parameter could be explained by density dependence. 4. Annual change in territory occupancy was linked to rainfall and temperature the preceding summer, after the main breeding season and to rainfall in the wintering grounds 24 months previously, coincident with the period of juniper Juniperus sp. (L.) flowering. High temperature in late summer, intermediate levels of late summer rainfall, and high spring rainfall in Morocco 24 months previously all had negative impacts on territory occupancy the following year. 5. All three weather variables have changed over recent decades, with a significant increase in summer temperature, a significant decrease in summer rainfall, and a nonsignificant decline in Moroccan spring rainfall. A model based on these trends alone predicted an annual decline in occupancy of 3.6% (compared with an observed decline of 1.2%), and suggested that increased summer temperatures may underlie declines in the British ring ouzel population. 6. Changes in summer temperature after the main breeding period could affect the survival rates of adult and/or juvenile birds. An improved understanding of the post-breeding ecology of ring ouzels is required to elucidate the mechanisms and causes of this relationship. Such knowledge might allow management aimed at buffering the impacts of climate change on ring ouzels.     

Nocturnal loss of body reserves reveals high survival risk for subordinate great tits wintering at extremely low ambient temperatures

Winter acclimatization in birds is a complex of several strategies based on metabolic adjustment accompanied by long-term management of resources such as fattening. However, wintering birds often maintain fat reserves below their physiological capacity, suggesting a cost involved with excessive levels of reserves. We studied body reserves of roosting great tits in relation to their dominance status under two contrasting temperature regimes to see whether individuals are capable of optimizing their survival strategies under extreme environmental conditions. We predicted less pronounced loss of body mass and body condition and lower rates of overnight mortality in dominant great tits at both mild and extremely low ambient temperatures, when ambient temperature dropped down to ?43 °C. The results showed that dominant great tits consistently maintained lower reserve levels than subordinates regardless of ambient temperature. However, dominants responded to the rising risk of starvation under low temperatures by increasing their body reserves, whereas subdominant birds decreased reserve levels in harsh conditions. Yet, their losses of body mass and body reserves were always lower than in subordinate birds. None of the dominant great tits were found dead, while five young females and one adult female were found dead in nest boxes during cold spells when ambient temperatures dropped down to ?43 °C. The dead great tits lost up to 23.83 % of their evening body mass during cold nights while surviving individuals lost on average 12.78 % of their evening body mass. Our results show that fattening strategies of great tits reflect an adaptive role of winter fattening which is sensitive to changes in ambient temperatures and differs among individuals of different social ranks.     

Goshawk predation during winter, spring and summer in a boreal forest area of central Sweden

Predation by goshawks was studied in a central Swedish boreal forest area. Data were collected in winter (January–February) 1977-81 by tracking radio-tagged goshawks, and in the breeding season (April–July) by collecting prey remains at the nest. In the breeding season birds dominated the prey, amounting to 86% of prey number and 91% of prey biomass. Wood pigeon Columba palumbus , black grouse Tetrao tetrix , hooded crow Corvus corone cornix and jay Garrulus glandarius accounted for more than 50% of the prey animals, whereas capercaillie Tetrao urogallus and black grouse accounted for more than 50% of prey biomass. There was no functional response to black grouse density fluctuations. Every year goshawks killed significantly more females than males of both capercaillie and black grouse, due to high vulnerability of the grouse hens while laying and incubating. It was estimated that during spring and early summer goshawk predation removed 25% of the female, and 14% of the male black grouse population. In winter squirrel was the dominating prey, both in terms of number (79%) and weight (56%). The proportion of squirrel in the diet was equally high both in winters of low and high squirrel density. The high proportion of squirrel in the winterdiet, as compared to the breeding season, is believed to be due to squirrels having to accept an increased predation risk in winter, in order to feed efficiently enough.     

WINTER SURVIVAL IN RELATION TO DOMINANCE CLASSES AMONG SILVEREYES ZOSTEROPS LATERALIS CHLOROCEPHALA OF HERON ISLAND, GREAT BARRIER REEF

Winter survival with respect to dominance classes of 932 individually colour-ringed Silvereyes was examined on Heron Island, Great Barrier Reef, between 1965 and 1969. The dominants (winning two-thirds or more of aggressive encounters) had significantly better chances of survival between May and August (southern winter) than other birds. The 1967/68 year group was studied in detail; the young born early in the breeding season contained proportionately more dominants than those born later in the season and dominant birds tended to survive better in winter. Adults in the same period showed no dominance dependent survival. The weight of birds in winter differed between first-year birds and adults in most cases, but winter mortality within each year-group was not related to the weight of individual birds in May. However, the dominant class had a smaller proportion of birds losing weight through the winter than other classes, and the dominant adults and the intermediate class of first-year birds tended to be heavier than others in August. The lengths of wing, tail, tarsus and exposed culmen examined for the 1967/68 year group showed no significant trends in either survival or dominance classes. Better survival of dominant birds is considered to be a consequence of their feeding advantages over others, but the intensity of selection for an ability for dominance may fluctuate from year to year in relation to the population density and distribution and abundance of food supply.     

Long-term hoarding in the Paridae: a dynamic model

Using stochastic dynamic programming we modeled the hoardingand foraging behavior of tits and chickadees, Pandas, that areresident in the boreal forest at high latitudes. Here autumnshave a rich supply of seeds and temperatures are relativelymild, while winters are cold with short days and a low foodsupply. We assumed that parids have a memory of limited durationand that forgotten seeds accumulate in a bank that adds to thegeneral food supply in the hoarder's territory. Our model predictsthat birds should start "high-intensity" hoarding in early autumn,but not before that. Because of mass-dependent costs the birdswill keep their fat levels low during the autumn. When winterarrives they will carry more body fat, both for the long winternights and to hedge against the large effects of weather variationsin winter. After increasing the fat level at the start of winter,fat should gradually increase even more, to compensate for thediminishing food supply. Most hoarding occurs in autumn as away of building up the supply of long-term stores. Remembered,or short-term caches, may hedge against stochastic events inthe environment. Even though conditions are not beneficial forhoarding in winter, the birds still stored in winter to maintainlarger short and long-term hoards if environmental variationincreased. Almost all time in winter that not was spent foragingwas spent perching, mainly to avoid predation     

THE WINTERING AND MOULT OF RUFFS PHILOMACHUS PUGNAX IN THE KENYAN RIFT VALLEY

Some 5700 Ruffs were ringed in the southern Kenyan rift valley during 1967–79, mainly at Lakes Nakuru and Magadi. These have produced 15 recoveries outside East Africa, 14 in Siberia between 73° and 154°E and one in India. Adult males returned to Kenya mainly during August, and females during late August and early September. Females greatly outnumbered males at all times. Most wintering males departed late in March and early in April, but females not until about a month later. First-year birds appeared from the end of August, but remained in low numbers until late October or November. Most departed during April and May, but a few females oversummered. First-year birds typically accounted for about 25% of the wintering Nakuru females, but about 50% of those at Magadi. At both sites they accounted for a higher proportion of male birds than females. Most of the birds at Nakuru throughout late August to May appeared to be local winterers, and many individuals remained in the area for many months each year. Retrapping indicated that approximately 60% of each season's birds returned the following season. Adult males and most adult females commenced pre-winter wing moult before arrival, but completed most of it in Kenya. Males moulted 3–4 weeks ahead of females, and most had finished before December. Females typically finished during December and early January. Most second year birds timed their pre-winter moult similarly to older adults. Suspension was recorded in over 15% of all moulting birds examined. Adult pre-summer moult involved most or all of the tertials, some or all of the tail feathers, most of the inner wing coverts and the body and head plumage. It occurred mainly during January to March (males) or February to April (females), although tertial renewal commonly began a month earlier. Males showed no sign in Kenya of the supplementary prenuptial moult. First-year birds moulted from juvenile into first winter body plumage during late September to November. They underwent a pre-summer moult similar in extent and timing to that of adults, and again about a month earlier in males than females. Spring feathers acquired were often as brightly coloured as those of adults. About 15% of first-year birds renewed their outer 2–4 pairs of large primaries during January to April. Adult and first-year birds fattened before spring departure, commonly reaching weights 30–60% above winter mean. Weights of adult males peaked early in April, those of adult females early in May, and those of first-winter females later in May. Weights were relatively high also during August and September. This was due to the arrival of wintering birds carrying ‘spare’ reserves, and also apparently to the presence of a late moulting fattening passage contingent. The wing length of newly moulted adults was about 3 mm longer than that of newly arrived first-year birds, but there was no evidence of an increase in the wing kngth of adults with successive moults. Adult wing length decreased by 4–5 mm between the completion of one moult and the middle stages of the next. The migrations and annual timetable of Kenyan wintering Ruffs are discussed, and their moult strategy is compared with that of other Holarctic waders.     

High site fidelity in Northern Wheatears Oenanthe oenanthe wintering in Africa revealed through colour marking

Wintering Northern Wheatears Oenanthe oenanthe in the Sahel region of Northern Nigeria held small (approximately 70?m diameter) distinct territories during the study period, and territory size did not differ between adult and first winter birds. Evidence suggests that Wheatears may maintain small territories for a significant duration of the winter, similar to many other migrants.