Jeffrey M. Black

Partnerships in birds : the study of monogamy

Initial Perspectives introduction - pair bonds and partnerships the battle of the sexes and the origins of monogamy the model family continuous partnerships long-term monogamy in a river specialist - the blue duck do barnacle geese benefit from life-long monogamy? mate fidelity in swans breeding partnership in two new world jays partnerships in promiscuous splendid fairy-wrens part-time partnerships divorce in the European blackbird mate fidelity and divorce in ptarmigan Causes and consequences of long-term partnerships in Cassins auklets monogamy in a long-lived seabird: the short-tailed shearwaters between and within-population variation in mate fidelity in the great tit monogamy in the sparrowhawk mate fidelity in penguins causes and consequences of mate fidelity in red-billed gulls dispersal, demography, and the persistence of partnerships in indigo buntings concluding Perspectives monogamy and sperm competition in birds mate fidelity and divorce in monogamous birds.

Parent-offspring relationships in wintering barnacle geese

The relationship between parent geese, Branta leucopsis, and their offspring was monitored in order to discover some of the possible costs and benefits resulting from their association. Compared with birds without young the amount of time parents devoted to feeding was restricted in autumn and winter when they spent significantly more time being vigilant and aggressive. Family goslings fed without interruption for longer periods in autumn, were victims of attacks less often and grew fatter than unattached goslings. By the time the geese migrated to the breeding grounds in spring over 60% of goslings were unattached. The appearance of unattached young was related to the frequency of parental attacks on them and to inter-sibling aggression. However, the majority of parents were still associating with at least some of their brood after 9–10 months. Birds with more breeding experience associated with offspring for longer. Maintaining association with offspring did not reduce a parents chances of surviving to, or breeding in, the following year. In fact, birds that remained with young for the longest period bred more successfully the next year than those with shorter periods of parental care. It is suggested that extended association with goslings may increase a parents chances of breeding in the future due to the ‘contributor’ effect of the goslings that stayed in the family. Such goslings spend more time being vigilant and repelling neighbours which enables parents to increase their feeding time.

Foraging dynamics in goose flocks : the cost of living on the edge

Abstract The effects of flock position on the foraging performance of individual barnacle geese, Branta leucopsis, were determined by comparing foraging behaviour, vegetation quality and diet of geese at the edge and centre of feeding flocks. Birds on the edge of flocks fed in a hurried fashion compared with centre positions (shorter bouts of foraging) probably because of the increased amount of vigilant behaviour and aggressive encounters. In energetic terms, however, the costs of grazing and vigilance balanced out, so that it was as ‘expensive’ to feed in either flock position. Geese appeared to obtain more food when in edge positions because they pecked faster and obtained more food per peck as a result of the higher biomass of grass. A series of calculations, which included measures of energy expenditure, gross intake and energetic quality of the food, showed that the net energetic payoff of birds in edge positions was substantially higher than that of those in the centre. The relative merits of taking positions in the flock edge for single geese, pairs and families are discussed. The finding that dominant families were most often in edge positions and avoided the centre, and the fact that families attacked neighbours more often than did any other geese, suggests that they actively attempt to monopolize the best food resource available to flock members which is usually on the edges of the flock.

Reproductive Performance and Assortative Pairing in Relation to Age in Barnacle Geese

1. The pattern of reproductive success (RS) in barnacle geese varied significantly as a function of age. RS continued to increase through the sixth year and peaked in the eleventh. It declined between the eleventh and fifteenth year. 2. The decline in RS in old age was not, as suggested by other workers, due to loss of mate and re-pairing with a young bird; individuals that retained their mates also had diminishing RS in the later years. 3. Low RS in the early years was attributable to the female. We suggest that this is because of inexperience in food and feeding area selection, which affects the build-up of body reserves in preparation for nesting and hence breeding potential. Low RS in the later years was, on the other hand, attributable to the male. We suggest that this is caused by a decline in fighting ability which determines both the acquisition of optimal feeding sites for the female and the ability to acquire and defend a nesting site. 4. At whatever age they re-paired, geese tended to choose replacement mates that were similar in age to themselves. This was despite the fact that, at all times, birds from the young, unpaired cohort (1-2 years) were considerably more numerous than older unpaired geese. 5. We argue that pairing with a familiar individual is advantageous both from the point of view of partner compatibility and of familiarity with the feeding and nesting habitat

Predator protection or similar habitat selection in red-breasted goose nesting associations: extremes along a continuum

Abstract We tested the predator protection and similar habitat hypotheses in relation to red-breasted goose, Branta ruficollis , nesting associations. Geese began laying 1–3 weeks after all associated species. In almost all cases they nested on the mainland only if raptors were also present and always followed raptors when they changed eyries between years. They selected peregrines, Falco peregrinus , and snowy owls, Nyctea scandiaca , as associates in preference to rough-legged buzzards, Buteo lagopus , even though the latter were several times more abundant along river corridors. Nest defence experiments with a surrogate Arctic fox, Alopex lagopus , showed that this could be explained by differences in nest defence intensity, rather than habitat types selected. Similar experiments also suggested that gulls were much less aggressive than owls or falcons. Foxes rarely approached, and were easily repelled from goose colonies associated with owls and peregrines, but gulls were apparently incapable of repelling foxes. Breeding success was much higher for geese nesting with raptors than for those on islands and geese apparently preferred to nest with owls in peak lemming years than to remain on islands. These findings support the hypothesis that red-breasted geese actively choose to nest near raptors; however, they probably associate with gulls primarily because both species select fox-free islands. Compared with other studies, red-breasted geese nesting with raptors and on islands apparently represent two extremes in a continuum of nesting associations generally seen in birds. We discuss why the behaviour might have evolved and argue that this may be the only known bird species whose evolution has been facilitated primarily by the exploitation of the nest defence behaviour of aggressive raptorial hosts. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.

The spring range of barnacle geese Branta leucopsis in relation to changes in land management and climate

This study examines recent changes in the distribution of spring staging barnacle geese Branta leucopsis in Norway. From the early 1980s onwards, two major changes have taken place. First, increasing numbers of geese moved from the traditional islands with a semi-natural vegetation towards agricultural fields on larger islands close to the mainland. Secondly, geese expanded their range by exploring more northerly located islands. Data on food exploitation by geese on the traditional islands were collected to interpret these changes. The density of shoots of edible grasses explained the spatial variation in grazing pressure over the traditional islands. This pattern was caused by intensive grazing of available habitat, where apparently a lower threshold of the intake rate set a limit to the amount of food cropped. It is concluded that the carrying capacity of the traditional islands had been reached. On many of the traditional islands, capacity declined, however, as the vegetation type with the highest density of grasses and most preferred by geese disappeared. This negative development seems to have started when people abandoned the islands and summer grazing by sheep stopped. The declining number of geese that can find sufficient food within the traditional range, in conjunction with the rapidly growing size of the total population, are the main causes for the observed expansion of the population. Increasing spring temperatures and a change in agriculture may have allowed the geese to move to the north, and to invade agricultural areas. To lessen conflicts between geese and farmers on the large islands, two lines of management are available: restoration of management on islands within the traditional range, and enhancing the attractiveness to geese of saltmarshes on the larger islands.

ADOPTION OF YOUNG AND INTRASPECIFIC NEST PARASITISM IN BARNACLE GEESE

Prior to use of genetic techniques, extra-pair copulations and intraspecific brood parasitism were rarely observed in long-term monogamous geese. DNA fingerprinting analysis of nine families of Barnacle Geese (Branta leucopsis) revealed one case of intraspecific nest parasitism with the offspring fathered by the attendant male, and one adoption of a foreign gosling. Observations showed that adoptions accounted for 5.8% and 24.6% of goslings hatched, or 13.3% and 24% of families in two successive years. Adoption appears to be common shortly after the young have hatched and has been assumed to result from accidental brood mixing when parent-offspring recognition is not yet fully developed. We found adoptions to occur in goslings as old as 4-12 weeks, when both parents and offspring are capable of recognizing each other, suggesting that accidental mixing alone cannot explain this phenomenon.

Staging of Pacific flyway brant in relation to eelgrass abundance and site isolation, with special consideration of Humboldt Bay, California

Spring distributions of black brant (Branta bernicla nigricans) are closely related to that of their primary food plant, eelgrass (Zostera marina).Using historical (1931–2001) brant data from Humboldt Bay, California, we show that proportional use of two main feeding areas in the bay strongly reflects food abundance.We used multiple regression to investigate whether the spatial relationship between brant and eelgrass holds at the flyway level.We related peak brant numbers at 11 staging areas in the Pacific flyway to the sites’ Z. marina abundance and isolation from other important staging areas.We explained 90% of the variation in peak brant numbers across sites with these variables; isolated bays with high eelgrass abundance supported the most brant.Our results emphasize the importance of protecting large eelgrass habitats along the Pacific Coast, particularly in bays that are geographically isolated from other large staging areas. # 2003 Elsevier Ltd.All rights reserved.

Behavioural syndromes in Steller's jays: the role of time frames in the assessment of behavioural traits.

Behavioural syndromes describe consistent and correlated individual differences in behavioural traits. Quantifying individual differences often requires researchers to capture and hold animals in captivity while short-term behavioural assays are recorded. We compared behavioural responses of adult, territorial Steller’s jays in short- and long-term field assessments of behavioural traits in two ecological contexts, risk taking and exploration. Individuals’ risk taking was similar in short-term and long-term contexts (i.e. alarm calling in the presence of a predator mount and while re-entering a trap, respectively). However, a measure of short-term exploration of a novel object in a feeding context was not related to a long-term index of annual habitat exploration (i.e. travel distance outside home territory). Risk-taking and exploration indices were correlated across ecological contexts, indicating that these traits contributed to a behavioural syndrome in jays. Annual assessments of risk-taking and exploration behaviours were repeatable. Individuals with high scores in risk taking and exploration were more likely to be recaptured in a familiar trap. We conclude that short-term experiments are adequate measures of specific behavioural strategies, but because short-term responses did not necessarily predict long-term annual behaviours in related contexts, expression of behavioural types and associated ecological strategies should be regarded as species and context specific. Long-lived residents are useful study species to overcome sampling biases for traits measured in captivity, because they provide opportunity to evenly sample a population over all personality types, including trap-shy individuals.

SLAVE TO THE TIDES: SPATIOTEMPORAL FORAGING DYNAMICS OF SPRING STAGING BLACK BRANT

Abstract Arctic-nesting geese depend on nutrients acquired during spring migration for reproduction, and thus should attempt to maximize nutrient intake while on staging areas. We investigated site use of Black Brant (Branta bernicla nigricans) at an important staging location—Humboldt Bay, California—to determine whether birds selected the most profitable feeding areas available. Migrating Brant feed almost exclusively on eelgrass (Zostera marina), which is restricted in availability due to daily and seasonal tidal cycles. We mapped foraging Brant locations during low tides and collected eelgrass samples to describe food resources in 31 areas in the bay. We used negative binomial regression to evaluate goose densities during different tidal levels and times of season as a function of food biomass and nutrient content, distance from grit sites, and substrate elevation. Results varied by time of season and tidal depth, but Brant densities were positively correlated with eelgrass protein, calcium, and biomass in most analyses. Brant usually fed in the deepest possible areas permitted by tides, and closer to tidal channels, where biomass and nutrient content of eelgrass were greater and where depletion from grazing was probably less. During higher low tides, Brant fed closer to previously visited grit sites. Tide cycles change over the course of the Brants staging period on the bay, enabling longer and more frequent access to deeper eelgrass meadows as spring progresses. These seasonal changes in tidal pattern coincide with seasonal changes in Brant use of the bay. Thus, migration patterns for estuarine bird species might be shaped by latitudinal gradients in both food phenology and seasonal tidal patterns.