Non-territorial Birds Research Articles

Neurogenomic landscape associated with status-dependent cooperative behaviour.

The neurogenomic mechanisms mediating male-male reproductive cooperative behaviours remain unknown. We leveraged extensive transcriptomic and behavioural data on a neotropical bird species (Pipra filicauda) that performs cooperative courtship displays to understand these mechanisms. In this species, the cooperative display is modulated by testosterone, which promotes cooperation in non-territorial birds, but suppresses cooperation in territory holders. We sought to understand the neurogenomic underpinnings of three related traits: social status, cooperative display behaviour and testosterone phenotype. To do this, we profiled gene expression in 10 brain nuclei spanning the social decision-making network (SDMN), and two key endocrine tissues that regulate social behaviour. We associated gene expression with each bird's behavioural and endocrine profile derived from 3 years of repeated measures taken from free-living birds in the Ecuadorian Amazon. We found distinct landscapes of constitutive gene expression were associated with social status, testosterone phenotype and cooperation, reflecting the modular organization and engagement of neuroendocrine tissues. Sex-steroid and neuropeptide signalling appeared to be important in mediating status-specific relationships between testosterone and cooperation, suggesting shared regulatory mechanisms with male aggressive and sexual behaviours. We also identified differentially regulated genes involved in cellular activity and synaptic potentiation, suggesting multiple mechanisms underpin these genomic states. Finally, we identified SDMN-wide gene expression differences between territorial and floater males that could form the basis of 'status-specific' neurophysiological phenotypes, potentially mediated by testosterone and growth hormone. Overall, our findings provide new, systems-level insights into the mechanisms of cooperative behaviour and suggest that differences in neurogenomic state are the basis for individual differences in social behaviour.

Responses of GPS-Tagged Territorial Golden Eagles Aquila chrysaetos to Wind Turbines in Scotland

Research on potentially adverse effects of wind farms is an expanding field of study and often focuses on large raptors, such as golden eagles, largely because of their life history traits and extensive habitat requirements. These features render them sensitive to either fatality (collision with turbine blades) or functional habitat loss (avoidance through wariness of turbines). Simplistically, avoidance is antagonistic to collision; although, the two processes are not necessarily mutually exclusive in risk. A bird that does not enter a wind farm or avoids flying close to turbines cannot collide with a blade and be killed. In the USA, collision fatality is implicated as the typical adverse effect. In Scotland, avoidance of functional habitat loss appears more likely, but this depends in part on the habitat suitability of turbine locations. Previous Scottish studies have largely concentrated on the responses of GPS-tagged non-territorial golden eagles during dispersal. Several arguments predict that territorial eagles may have lower avoidance (be less wary) of turbines than non-territorial birds. Hence, we contrasted the responses of GPS-tagged non-territorial (intruding) and territorial eagles to the same turbines at 11 operational Scottish wind farms. We show that territorial eagles rarely approached turbines, but, as in previous Scottish studies of non-territorial birds, the spatial extent of avoidance depended on the habitat suitability of both turbine locations and their wider surroundings. Unexpectedly, we found that territorial eagles were apparently as wary as intruding non-territorial conspecifics of the same turbines. Our results show that regardless of age or territorial status, Scottish golden eagles largely avoided wind turbine locations, but this avoidance was conditional, in part, on where those turbines were located. Responses to turbines were also strongly dependent on birds’ identities and different wind farms. We speculate on how widespread our findings of avoidance of turbines by golden eagles are elsewhere in Europe, where there appear to be no published studies showing the level of collision fatalities documented in the USA.

Foraging Patterns of Non-Territorial Eastern Imperial Eagle (Aquila heliaca): A Case of Successful Adaptation

The Optimal Foraging Theory predicts that, to maximize fitness, animals adapt their foraging strategy that provides the most benefit for the lowest cost, maximizing the net energy gained. While the diet of many breeding raptor populations is well known, studies on the foraging patterns of non-territorial birds of prey (floaters) are scarce. In this study, we examined the foraging pattern of non-territorial Eastern Imperial Eagle, scrutinizing different aspects of its feeding ecology and behavior. We built a simple model of the optimal foraging strategy of floater eagles including the success of foraging as a currency as well as environmental factors such as seasons, type of prey, habitat, foraging techniques, and eagle age as a limitation affecting the foraging efficiency of birds. We found that floaters focused their diet exclusively on European Souslik, accounting for almost half (44.2%) of the eagle’s prey. Diet differences between floaters and breeders were due to higher Souslik and carrion consumption and lower Hedgehog predation by floater eagles. The diet diversity of breeding eagles (H = 3.297) was much higher than that of floaters (H = 1.748). Our model suggested that the foraging mode, habitat type, and season best explained the feeding success of non-territorial eagles (ΔAIC = 0.00, w = 0.42). Of all explanatory factors, “Kleptoparasitism” (β2 = −4.35), “Rodents” (β2 = −4.52), “Pasture” (β2 = 2.96), “Wheat” (β2 = 4.41), “In the air” (β2 = 4.16), and “Other habitats” (β2 = 4.17) had a pronounced effect. The factors “Spring–summer season” (β2 = −0.67) and “European Souslik” (β2 = −2.76) had a marginal effect in our models. Generally, the mean success rate of attack modes used by non-territorial eagles was 0.54 ± 0.50. Floaters successfully obtained food through: kleptoparasitism (43.10%), carrion feeding (24.14%), and high soar with vertical stoop (14.66%). Several important issues for the conservation of non-territorial Eastern Imperial Eagles arose from our research. The strong relation of floaters with the European Souslik calls for specific conservation measures aimed at the conservation of this type of prey and the restoration and appropriate management of its grassland habitats. The importance of the scavenging behavior of juvenile birds requires increased control of the use of poison baits and subsequent prosecution by state institutions. Protecting the most important temporary areas, improving institutional control against the use of poison baits, and intensifying awareness-raising campaigns among pigeon-fanciers and hunters are also of crucial importance for effective species conservation.

Population responses to harvest depend on harvest intensity, demographics, and mate replacement in sandhill cranes

Recent examinations of hunting’s impact on populations of long-lived species illustrate the rarity of strong compensatory responses. The extent to which sandhill crane populations exhibit compensatory, partially compensatory, or additive responses to harvest mortality is poorly known. To examine how sandhill crane harvests might impact resident, breeding crane populations, we simulated harvests of a well-studied population of individually marked birds at varying harvest intensities and degrees of selectivity within the social structure of territorial and non-territorial cranes. Simulations occurred in a demographically-explicit stochastic population model developed from a previous long-term (2000–2014) study of a sandhill crane population at carrying capacity in southcentral Wisconsin, USA. Non-selective harvest models that did not account for reproductive lags after territorial birds replaced lost mates produced additive responses and resulted in declining populations when ≥ 7% of the population was harvested annually. When models of non-selective harvest incorporated reproductive lags, this threshold was reduced to ≥ 5%. Harvesting at or above 5% harvest intensities continuously decreased population size over a 100-year period. In all models of selective harvests, when only non-territorial birds were harvested, all populations returned to equilibrium. Population responses to harvest are sensitive to the number of territorial birds harvested, and this sensitivity increases when accounting for lags in reproduction stemming from mortality-induced mate replacement. If possible, limiting harvest of territorial birds from any one specific population would help maintain stability of populations when implementing a hunt. This study provides evidence for harvest impacts at a localized scale, and it represents an important first step toward better understanding the potential impacts of hunting on population responses at a regional scale, especially where resident, territorial birds might be harvested.

Spatial and temporal movements in Pyrenean bearded vultures (Gypaetus barbatus): Integrating movement ecology into conservation practice.

Understanding the movement of threatened species is important if we are to optimize management and conservation actions. Here, we describe the age and sex specific spatial and temporal ranging patterns of 19 bearded vultures Gypaetus barbatus tracked with GPS technology. Our findings suggest that spatial asymmetries are a consequence of breeding status and age-classes. Territorial individuals exploited home ranges of about 50 km2, while non-territorial birds used areas of around 10 000 km2 (with no seasonal differences). Mean daily movements differed between territorial (23.8 km) and non-territorial birds (46.1 km), and differences were also found between sexes in non-territorial birds. Daily maximum distances travelled per day also differed between territorial (8.2 km) and non-territorial individuals (26.5 km). Territorial females moved greater distances (12 km) than males (6.6 km). Taking into account high-use core areas (K20), Supplementary Feeding Sites (SFS) do not seem to play an important role in the use of space by bearded vultures. For non-territorial and territorial individuals, 54% and 46% of their home ranges (K90), respectively, were outside protected areas. Our findings will help develop guidelines for establishing priority areas based on spatial use, and also optimize management and conservation actions for this threatened species.

Ecology and behaviour of winter floaters in a subalpine population of Willow Tits, Poecile montanus

Willow Tits Poecile montanus maintain yearlong territories defended by a male and femalemated pair. Outside the breeding season the adult pair lives togetherwith two to four unrelated first-year Willow Tits that have settled after a post-natal dispersal. Because the habitat of the species is largely saturated with dominant territory owners and the flock size is limited, many juveniles fail to become resident flock members. These non-territorial birds behave as migrants during autumn or stay in the area for a short time (transients) or live as floaters that switch among flocks or roam about singly. The floaters (51 colourringed) and transients (450 colour-ringed) did not differ physically or in their foraging behaviour, whereas birds of these groups weremore vigilant and used less time for foraging than residents (114 colour-ringed). Floaterswere sociallydominated by residents and also maintained a poorer nutritional status. The mean wing length of males observed for the last time in November was significantly longer than that of those seen for the last time in September or October, whereas no such differences were found for body mass or nutritional status. The floatersmoved around solitarily and crossed several Willow Tit territories (males 2-8 territories, females 2-5 territories; mean territory size ca 25 ha). Only three male floaters settled, one disappeared in December the same year, one was seen for the last time in March and one in April the following year.

Size and Retention of Breeding Territories of Yellow-Billed Loons (Gavia adamsii) in Alaska and Canada

Yellow-billed Loons (Gavia adamsii) breed in lakes in the treeless Arctic and are globally rare. Like their sister taxa, the well-documented Common Loon (G. immer) of the boreal forest, Yellow-billed Loons exhibit strong territorial behavior during the breeding season. Little is known about what size territories are required, however, or how readily territories are retained from year to year. An understanding of territory dynamics and size is needed by management agencies as most of the U.S. breeding population of Yellow-billed Loons resides in the National Petroleum Reserve-Alaska where oil and gas development is expected to increase in the next few decades. Using locational data from a set of Yellow-billed Loons marked with satellite transmitters, we quantified an index of territory radius for each of three breeding populations: two in Alaska and one in Canada. The mean territory radius was 0.42 km for Yellow-billed Loons summering on lakes within the Seward Peninsula in northwest Alaska, 0.69 km for Yellow-billed Loons within the Arctic Coastal Plain of Alaska (encompasses the National Petroleum Reserve), and 0.96 km for Yellow-billed Loons within Daring Lake in mainland Canada. In this study, the mean territory radius on the Arctic Coastal Plain was about half the distance identified in stipulations for industrial development in the National Petroleum Reserve. The range in territory size among areas corresponded to a gradient in size of lakes used by Yellow-billed Loons with territories at the two Alaska sites on lakes averaging < 200 ha while territories in Canada were generally on much larger lakes. In the year after capture, 71% of Yellow-billed Loons retained territories that were held the previous year. Most Yellow-billed Loons that lost their territories wandered over a large area within 6 km of their prior territory. No Yellow-billed Loons occupied new territories, though one reacquired its prior territory after a 1-year hiatus. Retention of a territory in a subsequent year was positively related to early arrival dates at the breeding site. For Yellow-billed Loons on the Arctic Coastal Plain, this relationship was quite strong with a week lag in arrival decreasing the probability of retaining a territory by 80%. These collective observations, in combination with theoretical studies of population regulation by floaters (non-territorial birds), suggest that lake habitat suitable for breeding Yellow-billed Loons may currently limit population size in this species.

The role of season and social grouping on habitat use by Mute Swans (Cygnus olor) in a lowland river catchment

Capsule The Mute Swan, a large generalist herbivore, showed patterns of habitat use influenced by social grouping and season. Territorial swans showed strong preferences for river and lake habitat in all seasons, while the non-territorial birds known to cause grazing conflicts preferred river in summer–autumn and pasture in winter–spring. Aims To quantify the habitat preferences across different seasons of two types of Mute Swan social group, territorial and non-territorial, and assess the implications for the grazing conflict between swans and valuable plant communities. Methods Repeated surveys of the River Frome catchment, Dorset, UK, over a two-year period allowed us to record the numbers of swans in each habitat type. An electivity index was used to calculate habitat preference scores for territorial and non-territorial swans across different seasons. Results We found strong seasonal switches in habitat use for both territorial and non-territorial swans, but preferences for some habitats differed between these social groupings. In particular, non-territorial swans preferred pasture in winter and spring, and river in summer and autumn, while territorial swans preferred river and lake habitats throughout the year. Conclusion The Mute Swan, a large generalist herbivore that can cause grazing damage to river plant communities, showed patterns of habitat use influenced by social grouping and season. These seasonal patterns of habitat use suggest that the grazing conflict with the river plant community caused by flocks of non-territorial swans is currently limited to summer and autumn.

Territorial behavior of Western Sandpipers on their nonbreeding grounds: effect of sex and foraging interference

en

How Do Black-Tailed Gulls Respond to Long-Call Displays of Other Individuals?

Abstract Displays of animals do not always elicit equivalent responses from other conspecifics. Considerable variation exists among the responses, but the mechanism causing the variety remains unclear. We investigated how Black-tailed Gulls Larus crassirostris respond to long-call displays of other individuals. Results show that the response varies depending on the context. Territorial birds often respond to the long-calls of non-territorial birds by attacking. However, non-territorial birds typically respond to the long-calls of territorial birds by avoiding them. Nevertheless, they usually respond to the long-calls of their partners by using the same long-call. These results are explained well by the motivational conflict hypothesis.

Large scale risk-assessment of wind-farms on population viability of a globally endangered long-lived raptor

Wind-farms receive public and governmental support as an alternative energy source mitigating air pollution. However, they can have adverse effects on wildlife, particularly through collision with turbines. Research on wind-farm effects has focused on estimating mortality rates, behavioural changes or interspecific differences in vulnerability. Studies dealing with their effects on endangered or rare species populations are notably scarce. We tested the hypothesis that wind-farms increase extinction probability of long-lived species through increments in mortality rates. For this purpose, we evaluate potential consequences of wind-farms on the population dynamics of a globally endangered long-lived raptor in an area where the species maintains its greatest stronghold and wind-farms are rapidly increasing. Nearly one-third of all breeding territories of our model species are in wind-farm risk zones. Our intensive survey shows that wind-farms decrease survival rates of this species differently depending on individual breeding status. Consistent with population monitoring, population projections showed that all subpopulations and the meta-population are decreasing. However, population sizes and, therefore, time to extinction significantly decreased when wind-farm mortality was included in models. Our results represent a qualitative warning exercise showing how very low reductions in survival of territorial and non-territorial birds associated with wind-farms can strongly impact population viability of long-lived species. This highlights the need for examining long-term impacts of wind-farms rather than focusing on short-term mortality, as is often promoted by power companies and some wildlife agencies. Unlike other non-natural causes of mortality difficult to eradicate or control, wind-farm fatalities can be lowered by powering down or removing risky turbines and/or farms, and by placing them outside areas critical for endangered birds.

Interactions between harvesting, noise and territoriality in a model of red grouse population cycles

1. Population cycles are mostly thought to arise through extrinsic rather than intrinsic processes. However, in red grouse (Lagopus lagopus scoticus), intrinsic male territoriality has been proposed as a driver of the cycles, possibly in conjunction with an extrinsic interaction with specialist parasitic worms. Here we examine how harvesting and environmental noise may also interact with territoriality to determine how grouse populations cycle. 2. A stochastic model of grouse dynamics based on the territoriality hypothesis is developed, including harvesting and the effects of nonterritorial birds on aggressiveness. Cycles are detected in 97% of populations simulated over realistic parameter ranges, and these exhibit similar statistical properties to those reported in studies of multiple grouse populations. As observed, cycle periods are shorter at higher breeding productivities. 3. The model demonstrates the destabilizing influence of delayed density-dependent territorial aggressiveness. Cycle amplitudes are higher when annual changes in aggression are larger and when nonterritorial males provoke greater aggression. Intriguingly, the model suggests how an interaction between aggressiveness and parasites may operate. It is known that males with high worm burdens show dramatic decreases in aggressiveness in the year following a peak in territoriality. When this is included in the model, via larger crashes in aggression, amplitudes are higher, despite a reduction in overall aggressiveness. 4. Environmental stochasticity interacts with territoriality to determine the form of the cycles, but this is mediated through its 'colour' or temporal autocorrelation. For example, uncorrelated white noise increases amplitudes, while autocorrelated red noise has the opposite effect. However, noise increases cycle periods whatever the colour. 5. Harvesting occurs before territorial competition. This reduces the pool of males competing for territories and so increases recruitment and population densities. However, crashes can then be more extreme so cycle amplitudes are higher. With harvesting at ~150% of current typical levels, which is within observed variation, the dynamics exhibit a sharp transition to a state where cyclicity is reduced, periods are shorter and amplitudes lower. 6. The model suggests that to understand regional variation in red grouse cycles, interactions between territoriality, productivity, harvesting and noise must be considered.

Some an ± bn Problems in Number Theory

1. R. H. Lamberson and J. Carroll, Thresholds for persistence in territorial species, in Topics on Biomathematics, I. Varbieri, E. Grassi, G. Pallotti, and P. Pettazzoni, editors. World Scientific Publishing Co., Singapore, 1993, pp. 55–62. 2. R. H. Lamberson and S. J. Brooks, The role of nonterritorial birds in a population of northern spotted owls, unpublished technical report, Humboldt State University, Arcata, CA. 3. R. H. Lamberson, R. McKelvey, B. R. Noon, and C. Voss, A dynamic analysis of northern spotted owl viability in a fragmented forest landscape, Conservation Biology, 6 (Dec. 1992), 505–512. 4. R. Lande, Demographic models of the northern spotted owl (Strix occidentalis caurina), Oecologia, 75 (1988), 601–07. 5. T. Donovan, F. Thompson III, John Faaborg, and J.R. Probst, Reproductive success of migratory birds in habitat sources and sinks, Conservation Biology, 9 (Dec. 1995), 1380–95. 6. T. Donovan, R. H. Lamberson, A. Kimber, F. Thompson III, and John Faaborg, Modeling the Effects of Habitat Fragmentation on Source and Sink Demography of Neotropical Migrant Birds, Conservation Biology, 9 (Dec. 1995), 1396–1407.

Differential timing of spring migration in northern wheatears Oenanthe oenanthe: hurried males or weak females?

In a field experiment on the island of Helgoland (southeast North Sea), we investigated whether migration strategy or competition between the sexes cause the differential timing of spring migration of male and female northern wheatears (Oenanthe oenanthe) (males migrating earlier). The study included two subspecies, heading towards Greenland/Iceland and Scandinavia, respectively, and is based on colour-ringing and remote weighing of individuals. Despite food offered ad libitum, most Scandinavian birds left the island on the day of arrival or stayed only 1–3 days, whereas more than half of Greenlandic/Icelandic birds stayed for up to 12 days and refuelled rapidly. In the latter subspecies, males showed a positive correlation of departure fuel load and fuel deposition rate, resembling time-minimizers in optimal migration theory. In contrast, females departed irrespective of fuel deposition rate, with an approximately constant level of fuel stores. This level was lower than in males, but sufficient to enable by-passing of stopover sites en route, allowing us to regard females as time-minimizers also. Since females are not able to reach Greenland without additional refuelling elsewhere and males appeared to have a larger potential for by-passing stopover sites, time-selection seems to be more pronounced in males and may be the reason for earlier migration of males. Intraspecific aggressive interactions between colour-ringed birds were predominantly won by the initiator, by males and by larger birds, whereas fuel load and subspecies did not affect the outcome. Although compared to females, males were more often dominant at the feeding stations or held territories, refuelling patterns could not be explained by dominance. Subordinate or non-territorial birds did not refuel at a lower rate or depart with lower fuel loads than dominant or territorial birds. In non-territorial birds, the restricted access to feeding stations was made up with larger doses of food taken per visit, leading to the same energy intake as that of dominant and territorial birds. Therefore, competition during stopover could be eliminated as the reason for differential timing of migration of male and female wheatears, but this result may be species-specific.

Predicting the implications of conservation management: a territorial occupancy model of Bonelli's eagle in Murcia, Spain

Bonelli's eagle Hieraaetus fasciatus is a for the species. The model, which assumes demographic stability, estimates an equilibrium proportion of habitat threatened cliC-nesting raptor mainly distributed in the coastal regions of the Mediterranean. The European occupancy as a function of life history parameters, dispersal behaviour and habitat suitability. In spite of population has declined and the species is considered Vulnerable in Spain. Before eCective conservation pro- some limitations the model identified the most important conservation measures required for an increase in the grammes can be proposed the causes of this decline need to be considered. In a monitoring programme of the proportion of territories occupied: the improvement of the survival of both territorial and non-territorial birds, population of Bonelli's eagle in Murcia carried out since 1983 we observed a marked decline, followed by a period and an increase in the proportion of suitable habitat. of stability that began in 1990. Using demographic data (territorial bird survival, non-territorial bird survival, Keywords Bonelli's eagle, demography, Hieraaetus fasciatus, management, Mediterranean, Spain, survival, and fecundity) for 1990-1998 we applied a territorial occupancy model to evaluate management alternatives territorial occupancy model.

Seasonal Variation in Territory Occupancy of Non-Breeding Long-Billed Curlews in Intertidal Habitats

-During the non-breeding season, many shorebirds use coastal habitats where tides influence their dispersion patterns and social systems. We spot-mapped Long-billed Curlews (Numenius americanus) at the Elk River estuary, California to examine variation in territory occupancy from May 1999-April 2000. Curlew abundance was highest (a maximum of 16 territorial and up to 10 non-territorial birds) from July to September, after which time numbers declined progressively to 2-6 in winter. Five curlews were resident on >50% of observation days (N = 133) from June-April; these individuals returned to the estuary earlier and departed later than 11 other territorial curlews that were present 12-37% of occasions and mostly from July-November. Territory occupancy declined in association with precipitation and diurnal low tides ranging between -0.7 and 1.3 m. The absence of two territorial curlews coincided with rainy periods. The absence of curlews from five territories coincided with neap (low) tides; four of these curlews held territories at lower intertidal elevations with gently sloping topographies, such that they were inundated longer than other territories. At the Elk River estuary, territoriality may limit the number of curlews using intertidal habitats, but individual variation in territory residency suggests that numbers, and possibly carrying capacity, changed seasonally with availability of food in intertidal and pasture habitats. Habitat losses, such as those accompanying moderate (25-50 cm) rises in sea level associated with global warming, may reduce the carrying capacity of estuaries where existing levees preclude creation of new intertidal habitat. Received 31 October 2000, accepted 16January 2001.

Long-Term Study of Apparent Survival in Pacific Golden-Plovers at a Wintering Ground on Oahu, Hawaiian Islands

AbstractWe monitored the apparent survival of territorial and nonterritorial Pacific Golden-Plovers (Pluvialis fulva) for 20 consecutive nonbreeding seasons at a wintering ground within Bellows Air Force Station (BAFS) on the eastern shore of Oahu, Hawaii. Territorial birds were especially site-faithful from season to season, and each surviving individual reoccupied the same territory held in previous seasons. On average, territorial birds were resighted for about twice as many postbanding seasons (4.2) as nonterritorial birds (1.8). Open-population modeling indicated that apparent survival varied by age and territorial status. Our most parsimonious model estimated apparent annual survival rates in territorial plovers as 0.90 for young birds (age determined from retained juvenal primaries) from their first through their second wintering season, and 0.80 for adults over numerous seasons. For nonterritorial plovers, the corresponding values were 0.82 and 0.67, respectively. Despite lower apparent survival in nonterritorial plovers, it remains uncertain whether nonterritoriality actually results in shorter life spans. Some surviving nonterritorial birds may have gone undetected (detection probability of 0.70) because of permanent emigration from the study area. Given strong site-fidelity of territorial birds and the relative certainty of detecting them (probability = 1.0), we regarded the disappearance of a plover from its territory as an indicator of mortality. From last-recorded sightings, we concluded that territorial birds died with about equal frequency during the nonbreeding and breeding seasons. Because the latter is of much shorter duration, time-relative hazards were greatest while birds were away from the wintering grounds. Winter mortality was caused by accidents (collisions with overhead wires and other obstructions), and probable predation by owls. We estimated mean additional life expectancy among territorial plovers at 5.1 years for first-year birds, and 4.5 years for unknown-age adults. The oldest known-age individual was a male that lived 13 years 10 months; in adults of uncertain ages, one male survived to a minimum age of 18 years 10 months, and two females to at least 17 years 10 months. Pacific Golden-Plovers wintering at BAFS, especially territorial birds, demonstrated relatively high rates of apparent survival combined with adaptability for coexistence with humans in an urban environment.

LONG-TERM STUDY OF APPARENT SURVIVAL IN PACIFIC GOLDEN-PLOVERS AT A WINTERING GROUND ON OAHU, HAWAIIAN ISLANDS

Abstract We monitored the apparent survival of territorial and nonterritorial Pacific Golden-Plovers (Pluvialis fulva) for 20 consecutive nonbreeding seasons at a wintering ground within Bellows Air Force Station (BAFS) on the eastern shore of Oahu, Hawaii. Territorial birds were especially site-faithful from season to season, and each surviving individual reoccupied the same territory held in previous seasons. On average, territorial birds were resighted for about twice as many postbanding seasons (4.2) as nonterritorial birds (1.8). Open-population modeling indicated that apparent survival varied by age and territorial status. Our most parsimonious model estimated apparent annual survival rates in territorial plovers as 0.90 for young birds (age determined from retained juvenal primaries) from their first through their second wintering season, and 0.80 for adults over numerous seasons. For nonterritorial plovers, the corresponding values were 0.82 and 0.67, respectively. Despite lower apparent survival ...

MOVEMENT AND TERRITORIALITY OF WINTERING HERMIT THRUSHES IN SOUTHEASTERN LOUISIANA

We describe the spatial organization and social behavior of Hermit Thrushes (Catharus guttatus) wintering in pine plantations and an adjacent hardwood forest in Tangipahoa Parish, Louisiana over three winters. We used point counts (n = 403) to collect data on agonistic behaviors and relative abundance within the study area. We used mist-netting to study site fidelity on four 9-ha plots within and among years. We used radio-telemetry to measure Hermit Thrushes' movements and territoriality (n = 50). We found that Hermit Thrushes saturated suitable patches within the study area. Most Hermit Thrushes actively defended small [mean = 0.55 ± 0.03 (SE) ha], minimally overlapping (15.90 ± 3.63%) territories throughout the winter. Hermit Thrushes established and maintained territories using the same agonistic behaviors described for breeding birds. A few non-territorial birds (14%) moved among occupied territories, but most were faithful to a larger neighborhood, apparently awaiting a territory vacancy. Territorial behavior and frequency of non-territorial birds did not differ among age and sex classes, suggesting the absence of a sex- or age-based dominance hierarchy. The behavior of Hermit Thrushes conformed to the emerging view that competition for spatially mediated resources on the wintering grounds, such as food or cover, contribute to limiting populations of many species of migrant passerines.

Winter territoriality in migrant Black RedstartsPhoenicurus ochrurusin the Mediterranean area

The social organization and territoriality of a colour-ringed population of Black Redstarts Phoenicurus ochrurus was studied in a mountain area of southern Spain during 4 winters. A total of 28 adult males and 112 grey birds (females and juvenile males) was colour-ringed. These showed a complex territorial system: 5 adult males defended stable territories, 6 adult males and 1 grey bird temporarily defended different territories throughout the winter while most of the birds were non-territorial. Grey birds were observed less frequently than adult males in the area. Territorial and non-territorial birds seemed to be resident in the area; many being recorded after 40 days during the same winter. Territoriality was correlated with plumage and body size. However, size was age-dependent but within the group of adult males, there was no difference in either size, body mass or fat score suggesting no short-term benefits of being territorial. However, the survival rate seems to be higher for adult males than for grey birds according to the control of ringed birds in a subsequent winter. It is suggested that territoriality in adult males is a consequence of competition for certain resources (food or shelter areas) and this might affect the survival of different categories of birds.