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ABSTRACTTimed sea-watches were carried out at Holme Bird Observatory, Norfolk, UK, between May 2005 and December 2015. The rate of passage of 20 species was calculated as the number of birds passing the observation point per 10 hours. Analysis of the rate of passage by month enabled the species to be grouped into autumn passage migrants, summer visitors, winter visitors and species present throughout the year. There was no obvious spring passage of seabirds at the site. Wind strength and direction proved to be the most important environmental variables affecting seabird presence. Six autumn passage migrants (Manx Shearwater Puffinus puffinus, Gannet Morus bassanus, Great Skua Stercorarius skua, Arctic Skua Stercorarius parasiticus, Little Auk Alle alleand Kittiwake Rissa tridactyla) were most numerous when the wind was strong and northerly, conditions which favoured birds in the North Sea being blown towards the Norfolk coast. Two summer visitors (Sandwich Tern Thalasseus sandvicensisand Common Tern Sterna hirundo) were most numerous in weak winds and at low tide, conditions which may have favoured short feeding movements. Some species (e.g. Teal Anas creccaand Fulmar Fulmarusglacialis) were more numerous in the morning, but others (e.g. Kittiwake and Little Auk) were more numerous in the afternoon. Systematic observation over a 10-year period provided an enhanced understanding of the seasonal variation of different species seen offshore, and of the environmental factors that influence their movements.

Abstract: Demographic parameter estimates are essential for understanding population ecology and developing management plans for species of concern. We inferred measures of breeding success using radiotelemetry in the marbled murrelet (Brachyramphus marmoratus), a secretive, forest-nesting seabird, from 1998 to 2001 in Desolation Sound, British Columbia, Canada. Our estimates of mean annual nesting success and fecundity (0.19–0.23 female offspring/adult female/yr) are among the highest reported for the species. We suspect that our estimates are high compared to previous estimates in our study area (Manley 1999), primarily because of our higher success in areas inaccessible to ground-based human observers. We detail how behavior-based inferences of activity at different reproductive stages did not differ between confirmed nest sites and suspected nest sites that were physically inaccessible to us. We were able to accurately predict initiations of breeding and incubation success from the duration of adults' repeated daily shifts from the ocean to their inland nest sites. Chick-rearing success was accurately predicted by visitation rates of adults during provisioning. We discuss the assumptions and potential biases of our methods and their effects on our results. Our method may overestimate early breeding failure, but it likely provided unbiased fecundity estimates for our population. Accurately inferring breeding success through radiotelemetry is costly and labor intensive. However, radiotelemetry could provide crucial demographic information once thought impossible to obtain for secretive breeding species.

In einem großen Freiflugraum wurden jeweils acht ♂ und acht ♀ der Festlandrasse (Taeniopygia guttata castanotis) und der Inselrasse (T. g. guttata) des Zebrafinken zusammengebracht und die auftretenden Paarbildungen verfolgt. Im Verlauf des mehr als zweimonatigen Versuchs bildeten sich sieben Paare der Festland- und vier Paare der Inselrasse. Mischpaare wurden nicht beobachtet, obwohl am Ende unverpaarte Vögel nur der jeweils anderen Rasse als potentielle Partner zur Verfügung standen. Auch soziale Interaktionen zwischen den Rassen waren selten. Unter den halbnatürlichen Bedingungen des Experiments verhielten sich die beiden Rassen somit wie zwei getrennte Arten.

The potential contribution of early spring feeding conditions in the Arctic to clutch size variation was examined in a population of Lesser Snow Geese Anser caerulescens caerulescens. Behavioural observations were combined with energetic analyses of food material to derive an estimate of the energy budgets of pre-laying and laying females. Food intake of females between arrival on the breeding grounds and incubation was considerable; estimated energy gains in this period were in the same magnitude as the cost of one or several eggs. The pre-laying period spent on the breeding grounds can thus be energetically beneficial rather than costly. Accumulation of resources for reproduction in Snow Geese is a continual process including the breeding grounds, and nutrient limitation after arrival in the Arctic cannot sufficiently explain the environmental component of clutch size variation. The timing of migration and follicle development is such that clutch size decisions are sometimes made during the late stages of migration and some-times after arrival. In the latter case food conditions on the breeding grounds may greatly influence clutch size; in the former case they may still influence readjustments of clutch size after the initial decision. The universal negative correlation between clutch size and laying date in Snow Geese can be explained by negative fitness consequences of late hatching, which outweigh the benefits of delayed laying and further nutrient accumulation. Food shortage on the breeding grounds may sometimes be a secondary factor contributing to seasonal clutch size decline.

The photoresponses of natural populations ofD. pseudoobscura andD. persimilis, occurring sympatrically, are measured in two environmental conditions (“at rest” and “disturbed”). Comparisons of the responses, intraspecifically and interspecifically, lead to the following conclusions. These must be considered within the confines of the operational nature of the measurement of laboratory photoresponses. (1) Within each species population, significant nonenvironmental differentiation has been allowed or produced by selection in the “at rest” photoresponse. No significant nonenvironmental differentiation is found in the photoresponse measured in a disturbed condition. (2) Within each species population, a higher mean “disturbed” photoresponse has been favored. The intensities or patterns of selection acting on these two photoresponses have differed such that more intrapopulation differentiation has been allowed or produced in the “at rest” photoresponse. (3) A higher mean photoresponse has been favored inD. persimilis for both conditions. The intensities or patterns of selection acting between these two species populations on the “at rest” photoresponse have differed such that more intrapopulation differentiation has been allowed or produced inD. persimilis. (4) Comparisons of this study with one on intraspecific and interspecific differentiaiton in wing length lead to the conclusion that the selective differences inferred above have acted at a level more specifically attuned to photobehavior.

A maximum of 22 bands comprising four esterase subgroups—acetylesterase, carboxylesterase, cholinesterase, and acetylcholinesterase—were detected following electrophoresis of lesser snow goose sera on polyacrylamide gels. A minimum of seven structural genes was surmised to be involved in the biosynthesis of these enzymes following physiochemical characterizations. The genetic variability of these loci was calculated to be 1.25% average heterozygosity, while 14.3% of the loci were polymorphic. These estimates of genetic variability were substantially lower than those reported for other vertebrate species. The low degree of genetic variability found in snow goose serum esterases coupled with the extensive protein multiplicity observed may possibly reflect an adaptive strategy based on “biochemical plasticity” rather than genic heterozygosity for this species. The nature of evolutionary forces acting upon multiple enzyme systems such as esterases is discussed. The concept of “conditional neutrality” is introduced and defined within this context.

The reproductive efficiency, defined as the number of breeding recruits produced per egg laid; of intraspecific nest parasites; of hosts in parasitized nests; and of unparasitized nesting females, was measured for 14 years for lesser snow geese Anser caerulescens caerulescensnesting near Churchill, Manitoba, Canada. Relative efficiencies were 0.71–0.88, 0.91, and 1.0 for eggs of parasites, hosts, and unparasitized birds, respectively. Differences in the hatching probabilities of the three classes of eggs produced the efficiency differences. Parasitic success was limited by the parasites' failure to place more eggs than expected by chance into nests at the appropriate time relative to host incubation. Host nesting success was lower when more than one parasitic egg was added to the clutch. No differences in gosling survival and breeding recruitment probabilities were detected among any categories of goslings. Thus, hatching parasitic young are at no disadvantage relative to parental young, and there is no support for the hypothesis that increased success of host young at later stages of reproduction might offset negative effects at the egg stage. The hatching efficiency of parasitic eggs declined more rapidly than that of parental eggs as the parasitism rate increased. Efficiencies were similar when 3–4% of the eggs laid per year were parasitic, but relative parasitic efficiency was significantly lower when the parasitism rate was 8–9% or more. Using ancillary information and assumptions about the fecundity, viability, and behavioral flexibility of parasitic and parental females, we conclude that intraspecific nest parasitism could compete with nesting as a reproductive strategy in this population. The conditional use of parasitism by a large component of the population in certain years, however, combined with negative‐frequency dependent success, limits the potential spread of a purely parasitic strategy in this population.

The investigated the hypothesis that positive assortative mating for plumage coloration observed in populations of the dichromatic Lesser Snow Goose (Anser caerulescens caerulescens) evolved and persists due to selective advantages accruing to individuals choosing mates phenotypically similar to themselves. We examined potential differences between pure (white × white, blue × blue) and mixed (white × blue, blue × white) pairs for an array of fitness components related to both fecundity and viability. While no differences were detected for most components, mixed pairs consistently enjoyed enhanced nesting success relative to their pure counterparts. In addition, pre‐reproductive viability and female offspring recruitment were significantly greater for mixed pairs for some of the cohorts examined. Not only have we failed to find enhanced reproductive success associated with positive assortment, we have provided evidence that there is some advantage associated with negative assortment. In light of our findings, we suggest: 1) that positive assortment results from the use of familial color as one element in species recognition; 2) that the enhanced fitness of mixed pairs, particularly with respect to nesting success, results from complementation of parental behavior; and 3) that while negative assortment will not likely become the rule in this population, the selective advantage of mixed pairs is a potential determinant of pair type frequencies in the La Pérouse Bay population.

Different mechanisms proposed to explain the intra-seasonal decline in clutch size of Lesser Snow Geese (Anser caerulescens caerulescens) were tested at the La Perouse Bay colony, Manitoba, Canada. Ovary examination of females collected after laying revealed that the actual number of eggs produced per female decreased over the laying period. This finding eliminates nest-parasitism, partial clutch predation and renesting attempts as sufficient explanations for seasonal clutch size decline. Follicular atresia induced by reserve depletion was also rejected since its occurrence was similar among early and late nesters. The decline in clutch size was observed within age-classes, and therefore age effects on clutch size and laying date per se do not account for the observed relationship. Clutch size and laying date were respectively positively and negatively correlated with the amount of nutrient reserves in females at the onset of laying, and also covaried within individuals observed breeding in several seasons. Laying date repeatability was estimated at 0.22. It is postulated that the seasonal decline in clutch size results mainly from a positive feed-back of female's nutrient reserves on the hormones controlling ovary development. Hatching synchrony or shortness of the breeding season may be the ultimate factors responsible for the intra-seasonal clutch size decline in Lesser Snow Geese.

In many species, fecundity is dependent on age. For some populations — particularly those exploiting temporally variable environments — these age-specific fecundities may themselves vary with time. In this report, we investigate the general effects of age and time on clutch size in a wild population of Lesser Snow Geese (Anser caerulescens caerulescens). We show that both factors affect clutch size independently. Age effects are confined almost exclusively to the two, three and four year old age classes. Mean clutch sizes of all age classes show considerable inter-seasonal variation. These temporal differences in fecundity will ultimately influence the dynamics of the population. In particular, they imply that there will be no convergence to a constant growth rate or a stable age distribution.

Cooch (1961, 1963) suggested that changes in the genotypic composition of snow goose colonies comprising the Hudson Bay‐Foxe Basin population could be attributed to selection favoring the blue phenotype. In the preceding paper (Cooke et al., 1985), we examined potential differences in net fecundity between the two phenotypes at La Pérouse Bay in northern Manitoba. No substantial differences in any component of fecundity were detected. In the present paper, we examined potential differences in pre‐reproductive and adult viability, age of maturation, and breeding propensity. Again, no differences associated with the plumage polymorphism were detected in any of these life history characteristics. Thus, despite a thorough analysis of the complete life cycle, we were unable to uncover any evidence supporting a selection hypothesis for the persistence and dynamics of this conspicuous polymorphism. An alternate hypothesis based primarily on gene flow and assortative mating appears more plausible.

Between 1969 and 1977 the frequency of the blue phenotype of the dimorphic Lesser Snow Goose (Anser caerulescens caerulescens) showed a steady increase at the La Pérouse Bay colony near Churchill, Manitoba. Cooch (1961, 1963) suggested the global increase resulted from selection pressures favoring blue individuals. The selection hypothesis was evaluated by examining phenotypic differences in net fecundity. We partitioned the reproductive cycle into a series of stages, each defined by a particular index of fecundity. Despite large samples we were unable to detect any significant differences between the two maternal phenotypes in those indices that could conceivably influence population dynamics. We cannot, however, dismiss selection as the mechanism of population change, nor as a contributor to the maintenance of the polymorphism without assessing potential phenotypic differences in viability, age of maturation, and breeding propensity. These attributes are examined in the following paper (Rockwell et al., 1985).

The determination of the degree of genetic relatedness among individuals is important for many population and behavioural studies1. Conventional genetic markers such as allozymes are usually inadequate for such determinations, especially in avian species2,3. Restriction fragment length polymorphisms (RFLPs) which are inherited as co-dominant mendelian alleles4, have recently been applied to paternity and maternity analyses in humans to address both medical diagnostic and legal5issues. Field observations have led to the suggestion that lesser snow geese (Anser caerulescens caerulescens) engage in intraspecific brood parasitism (IBP)6and extra-pair fertilization (EPF)7. Direct evidence for these suggestions has been difficult to obtain because of the lack of easily detectable genetic markers8. We have recently prepared a recombinant genomic library from the lesser snow goose and isolated seventeen probes that all identify RFLPs9. Here we use some of these polymorphic loci to examine the relatedness among members of four families. This study provides evidence for mixed maternity and paternity in broods of this socially monogamous species and demonstrates the utility of DNA markers for genetic analyses of species which traditionally exhibit few conventional genetic markers.

Nesting female lesser snow geese (Anser caerulescens caerulescens) usually adopt eggs that are laid adjacent to their nests by potential intraspecific nest parasites. The host female rolls the parasite’s egg up into the nest, using the same behavior patterns used to retrieve her own eggs if they are displaced from the nest. The reproductive consequences of adopting eggs are unclear. We consider three selective scenarios that might maintain adoption behavior in geese: (1) egg adoption is of no reproductive consequence to the host; (2) egg adoption augments host reproductive success relative to that of unparasitized nests; and (3) egg adoption is making the best of a bad situation, once a female’s options are constrained by the presence of an egg adjacent to the nest; we also consider (4) the possibility that adoption, if not concordant with the selective regime, is maladaptive. Nest parasitism is costly to the host, making hypotheses 1 and 2 unlikely. However, adopting eggs significantly decreases the risk of total nest failure during laying, more than offsetting other probable host costs. This is consistent with hypothesis 3. Experiments show that geese have limited abilities to retrieve eggs, which accounts for most cases of nonadoption of nearby eggs. We conclude that adoption of eggs is an adaptive trait, a form of nest protection. Adopting eggs is the best option within the species’ repertoire to the threat to nest survival created when a parasite lays an egg next to the nest. [Behav Ecol 1991;2:181-187]