Using logistic regression models to predict breeding success in male Adélie penguins (Pygoscelis adeliae)

Measures of breeding success are traditionally derived using the proportion of total nests that successfully reach strategic stages across a breeding season, such as pair formation, egg laying or fledging chicks. The use of logistic regression has recently become a popular tool in avian literature for identifying influential factors that predict nest and/or individual breeding success. In this study, we use logistic regression models to assess the importance of a range of factors affecting male Adélie penguin (Pygoscelis adeliae) breeding success during the 2002–2003 austral summer, when the presence of icebergs and extensive sea-ice meant overall breeding success of Adélie penguins was low (16/51 focal males had chicks reach fledging point). Logistic regression models for the early breeding season showed that good/average nest quality and central/middle nest location within the sub-colony were the best predictors of successful pair formation. Later, during incubation, the most successful males were those that not only returned earlier but were also heavier upon arrival and built nests of at least average quality. During the final stage when chicks had begun to fledge, the combined parameters of heavier male weight, early arrival time and good nest quality were the best predictors of breeding success. The logistic regression approach used here showed that the predictive ability of these parameters varied as the season progressed. However, most importantly, our logistic models fit the data well across all breeding stages.     

BIOLOGY AND BEHAVIOUR OF FRIGATEBIRDS FREGATA SPP. ON ALDABRA ATOLL

Both species nested in mixed colonies in mangrove trees. The tops of trees were usually occupied exclusively by minor and the lower parts by ariel, but most nests of both species were in the intermediate parts of the canopy. The main laying season for both species was July to January. A census showed about 27 000 individuals present at the height of the season (1500 breeding pairs of minor, 5350 of ariel). Seasonal variation in numbers could be accounted for almost entirely by the changes in breeding activity of a resident population. Young of both species were fed at or near the nest-site for at least four months after fledging. A recovery near Bombay of a wing-tagged immature ariel shows that this species, at least, undergoes a post-fledging dispersal; it is suggested that young minor either do not disperse, or do so later than ariel. Food samples collected from chicks showed no overall difference between the species, but a seasonal analysis showed that ariel took more squid than minor in the wet season, and in the dry season the two species took different proportions of the two commonest species of flying-fish. Chicks of ariel received smaller meals than minor chicks in the wet season, but similar-sized meals in the dry season; ariel chicks grew more slowly than minor chicks. It is suggested that the timing of the breeding season is related to the need for adults to build up fat reserves to carry them through the courtship, nest-building and laying periods, when they are tied to the colony and so have little opportunity to feed. The evidence for non-annual breeding in frigatebirds is discussed. It is concluded that while successful breeders must breed at intervals of more than 12 months, they could theoretically nest in two successive seasons and that, since breeding success is low, most individuals probably do so. Existing knowledge of the biology of four of the five recognized species of frigatebirds is summarized, and shows that the family is at least as uniform as the tropicbirds and much more so than other Pelicaniformes.     

On the demography of Rattus sordidus colletti in monsoonal Australia

Results of a mark-release study of Rattus sordidus colletti (Gould) on sub-coastal, treeless plains in the monsoonal north of the Northern Territory of Australia are given for 5 years. R. s. colletti is the dominant component of the small mammal fauna of these plains, with only small numbers of Melomys spp. and Planigale maculata also occurring. Two classes of peak densities were observed. Localized peaks resulted from non-breeding adult R. s. colletti refuging onto the marginally higher levees during flooding of the plains, and also from refuging into a lower-lying area at the end of a dry-season drought. Generalized peak densities resulted from peaks in reproductive effort. In 1972 and 1974, reproduction was confined to the period immediately following the monsoons, but in 1973 breeding continued throughout the dry season, following unseasonal rain in June. Thus, generalized peak densities were observed in one year at the beginning of the dry season, and in another at its end. The relatively shallower flooding and mildness of the 1972–3 wet season resulted in commencement of breeding earlier in 1973 than in 1974, while rapid severe flooding of the plains in December 1974 resulted in mass mortality and failure of the refuging populations of adults to recolonize the lower plains in 1975. R. s. colletti remained extremely rare until November 1976, when the study was terminated. The good conditions which allowed reproduction during the dry season of 1973 were reflected in rapid growth rates at that time, compared with rates approaching zero in the 1974 dry season. R. s. colletti is the most fecund form of Australian Rattus species. This high fecundity appears to compensate for the restriction, by dry-season aridity and wet-season flooding, of the breeding season in most years to a short period immediately following the monsoons. In unusual years with rainfall during the dry season, the high fecundity gives R. s. colletti populations the capacity to reach very high densities.     

Blue penguin (Eudyptula minor) nest distribution and breeding success on Otago Peninsula, 1992 to 1998

Abstract

Annual counts of nests with eggs or chicks (known nests) were made at blue penguin (Eudyptula minor) breeding sites on the Otago Peninsula in each November from 1994 to 1997. Although the population has doubled to an estimated 600 known nests over this period, the number of breeding sites on the Otago Peninsula has reduced since the 1970s. Breeding success at three areas at Taiaroa Head were monitored by regular nest checks in the breeding season from 1992 to 1998. At Taiaroa Head reproductive success ranged from 41 to 78% at the three sites during the seven‐year study and was generally higher for pairs nesting in nest boxes than for those in burrows. The percentage of breeding pairs that laid a second clutch after fledging at least one chick from their first clutch (double brooded) varied between seasons (0–48%) and was correlated with the date of the onset of breeding. Egg loss, possibly through predation by Norway rats (Rattus norvegicus), influenced the significantly lower reproductive success at one area (Area A) at Taiaroa Head during the 1996 season.     

Seasonal sex role changes in the blenniid Petroscirtes breviceps, a nest brooder with paternal care

The plasticity of the sex roles in the blenniid fish Petroscirtes breviceps , a nest brooder with exclusive paternal care, was studied throughout an 8 month breeding season. Males performed most courtships early and late in the breeding season, whereas females performed most in the middle of the season. These results indicated that the sex of individuals initiating courtship changed seasonally, with courtship role reversal in the middle of the season. Intrasexual aggression in both sexes occurred much more frequently in mid-season than in the early and late seasons. Males frequently fought when available nest sites were limited, regardless of the presence of females, suggesting that males competed for nests in order to qualify to mate (resource competition). In contrast, courting females fought only in mid-season, when females' relative success in entering nests decreased, indicating that females competed for limited mating opportunities (mating competition). The reversed courtship roles and female mating competition in mid-season suggested that the sex roles in P. breviceps changed seasonally from the conventional roles to reversed roles and back again during one breeding season. This study provides the first empirical evidence of multiple changes in the sex roles of animals within a breeding season.     

Prolactin and parental behavior in Adélie penguins: effects of absence from nest, incubation length, and nest failure

Adélie penguin (Pygoscelis adeliae) males and females, nesting in Antarctica, alternate attendance at the nest with absences of many days to forage at sea. We investigated the importance of tactile input from egg and chicks on prolactin levels by observing nest attendance patterns and obtaining blood samples (1) during the first nest exchange of the incubation stage, (2) from birds whose incubation period was artificially increased or decreased by about 10 days, and (3) from birds whose nests had failed. Prolactin levels in females after 8 to 11 days of absence from the breeding colony did not differ from those in incubating males and did not change after females resumed incubation. Moving eggs between nests resulted in nests in which chicks hatched after about 26, 36 (normal), or 46 days. Duration of incubation did not affect prolactin levels in the parents measured during incubation, at the pip stage, hatch stage, or early brood stage. Adults first left their chicks unguarded on about the same calendar date, regardless of chick age. However, chicks from long incubation nests averaged 8 days younger when they were left unguarded than chicks from control or short-incubation nests. In females, there was no effect of nest failure on prolactin levels. In males, prolactin levels were slightly lower after nest failure than in males tending nests. Testosterone was significantly higher in males after nest failure than in males still tending nests. Prolactin is elevated in Adélie penguins as part of the program of cyclical hormonal changes that accompany the lengthy reproductive season and is relatively independent of tactile input. Sustained prolactin secretion is probably required for the maintenance of parental behavior in offshore feeding species that must be absent from the nest for many days at a time.     

Testing the importance of nest concealment: does timing matter?

ABSTRACT.   Nest concealment by vegetation is considered an important factor affecting predation rates for many passerines and, therefore, is frequently measured in studies examining nest predation. However, the time when concealment measurements are made may affect the results of such studies, particularly in highly seasonal ecosystems where characteristics of the vegetation later in the breeding period may differ considerably from those at the time of nest-site selection. We used artificial nests baited with quail ( Coturnix sp.) eggs in a highly seasonal tropical dry forest in Jalisco, western Mexico, to test the effects of seasonal change in concealment on nest predation. We placed 40 open-cup, artificial nests in shrubs at the end of the dry season and again at the beginning of the rainy season in 2007, and monitored the fate of the nests and the degree of concealment by vegetation during both periods. Nest concealment was significantly greater during the wet season than during the dry season. The percentage of nests predated was marginally higher during the dry (100%) than the wet (72.5%) season, and daily nest survival was lower during the dry than the wet season. Our results suggest that, in highly seasonal environments such as tropical dry forests, delayed measurement of nest concealment after nest completion rather than during nesting may constitute a significant source of error.     

Kori bustard (Ardeotis kori struthiunculus) occurrence in the Serengeti grass plains,northern Tanzania

The kori bustard (Ardeotis kori struthiunculus) is indigenous to grasslands and lightly wooded savannahs of southern and eastern Africa. The species is categorized as near threatened in its entire range due to anthropogenic factors and low reproductive rates. The aim of this study was to analyse the impact of grass colour, grass height, season and location on the density/occurrence of this bird species in the Serengeti grass plains, Tanzania. Data were collected from January 2014 to June 2015 using transect counts in four seasons: (i) short dry, (ii) long rain, (iii) long dry and (iv) short rain seasons, respectively. The mean density of kori bustard in the grass plains was 0.25 ± 1.01 per 0.2 km² with near‐significant differences among the study sites. The occurrence of kori bustard was high in the medium height (11–30 cm) during the long rain and short dry seasons. The kori bustard density is relatively low, and the distribution varies with grass height and season. We suggest that conservation efforts should be directed at preventing its local extinction by protecting the habitat from excessive human activities, such as livestock grazing and illegal offtake.     

Mate Choice and Mating Pattern in a Stream Goby of the Genus Rhinogobius

The mate choice and mating pattern of a benthic goby Rhinogobius sp. CB (cross band type) were investigated in the Kamo River, Shikoku, Japan. During the breeding season, gravid females assumed a nuptial color and either males or females initiated a courtship display. Males preferentially courted a female of similar size to lead her to his nest, whereas females courted more frequently when they encountered a large male. Eggs in any one nest were always at the same developmental stage. Sampling data of nesting males and females indicated that, in more than half the nests, males gathered more than one female before spawning. In some nests with eggs, two or three females had spent ovaries, indicating that the eggs were laid by multiple females within a short span of time. However, a comparison between the total number of eggs which females would spawn in one nest and the number of eggs actually deposited suggested that eggs were contributed by one female in most nests. This low level of polygyny in spite of multiple female availability is attributed to a limited available spawning area of the nest.     

Testing hypotheses about the function of repeated nest abandonment as a life history strategy in a passerine bird

Nest structures are essential for successful reproduction in most bird species. Nest construction costs time and energy, and most bird species typically build one nest per breeding attempt. Some species, however, build more than one nest, and the reason for this behaviour is often unclear. In the Grey Fantail Rhipidura albiscapa, nest abandonment before egg‐laying is very common. Fantails will build up to seven nests within a breeding season, and pairs abandon up to 71% of their nests before egg‐laying. We describe multiple nest‐building behaviour in the Grey Fantail and test four hypotheses explaining nest abandonment in this species: cryptic depredation, destruction of nests during storm events, and two anti‐predatory responses (construction of decoy nests to confuse predators, and increasing concealment to ‘hide’ nests more effectively). We found support for only one hypothesis – that abandonment is related to nest concealment. Abandoned nests were significantly less concealed than nests that received eggs. Most abandoned nests were not completely built and none received eggs, thus ruling out cryptic predation. Nests were not more likely to be abandoned following storm events. The decoy nest hypothesis was refuted as abandoned nests were constructed at any point during the breeding season and some nests were dismantled and the material used to build the subsequent nest. Thus, Grey Fantails are flexible about nest‐site locations during the nest‐building phase and readily abandon nest locations if they are found to have deficient security.     

Drivers of the breeding success of American Oystercatchers (Haematopus palliatus frazari) at a critical site in Sinaloa,Mexico

Understanding breeding phenology and success can elucidate population dynamics, which is especially important for species in need of conservation. We describe the factors affecting the breeding biology of American Oystercatchers (Haematopus palliatus frazari) at El Rancho Island, a critical site that contains ~ 7% of the total estimated population, on the coast of Sinaloa, Mexico. We monitored 192 nests over four years (2016–2019). The breeding season lasted from March to June and mean laying dates differed among years, with the mean laying date in 2019 an average of 20 days earlier than in 2016. Clutch sizes decreased as the breeding season progressed. Both breeding success and productivity differed among years, with the lowest values in 2016 (30% hatching success and 0.6 chicks/nest) and the highest in 2019 (66% hatching success and 1.2 chicks/nest). Hatching success was affected by year, laying date, type of habitat, and distance to the high tide line. American Oystercatchers that laid eggs earlier in the season, used mixed marsh and dune habitat, and with nests relatively close to the waterline (< 50 m) had greater breeding success. Overall, however, the breeding success of American Oystercatchers was low and influenced by a combination of several intrinsic and extrinsic factors. Management measures may be required to increase breeding success and ensure the conservation of this subspecies.     

Predator presence may benefit: kestrels protect curlew nests against nest predators

We studied whether the presence of breeding kestrels (Falco tinnunculus) affected nest predation and breeding habitat selection of curlews (Numenius arquata) on an open flat farmland area in western Finland. We searched for nests of curlews from an area of 6 km² during 1985–1993. For each nest found, we recorded the fate of the nest, and the distance to the nearest kestrel nest and to the nearest perch. We measured the impact of breeding kestrels on nest predation by constructing artificial curlew nests in the vicinity of ten kestrel nests in 1993. Curlew nests were closer to kestrel nests than expected from random distribution, eventhough kestrels fed on average 5.5% of curlew chick production. Predation risk by kestrels was lower than predation risk by corvids and other generalist predators, which predated 9% of curlew nests surviving farming practices and an unknown proportion of chicks. Artificial nest experiment showed that nest predation was lower close to kestrel nests than further away suggesting that the breeding association of curlews and kestrels was a behavioural adaptation against nest predation. Thus, the presence of a predator may sometimes be beneficial to prey, and prey animals have behavioural adaptations to these situations.     

Habitat suitability and demography,a time‐dependent relationship

The habitat suitability index, which reflects spatial variability in species occurrence probability, has been shown to exhibit various contrasting relationships with local demographic performances (survival, productivity) in several species. One proposed explanation for these discrepancies is that the link between the habitat suitability index and demography is influenced by density‐dependent, temporally variable processes. Based on the survival rates of more than 3,000 nests monitored over 12 years in the North African Houbara Bustard, we investigated whether the habitat suitability index computed over the species breeding range is related to nest survival throughout the breeding season, accounting for variation in meteorological conditions. We found that the relationship between the habitat suitability index and nest survival progressively changes along the breeding season and that this intra‐annual variation is consistent between years. Our results support the hypothesis that variation in space use occurs intra‐annually and that biotic interactions throughout the breeding season strongly influence the habitat suitability index–demography relationship.     

Breeding of the lappet-faced and white-headed vultures (Torgos tracheliotus Forster and Trigonoceps occipitalis Burchell) on the Serengeti Plains, Tanzania

The lappet-faced and white-headed vulture nests in a 1636 km² study area on the Serengeti Plains were kept under observation from June 1972 to August 1973. Active nests were inspected from a light aircraft at intervals of approximately 2 weeks. The inverse nesting densities were estimated as 43 km²/pair for the lappet-faced vulture and 409 km²/pair for the white-headed vulture. Nests were built of sticks in exposed sites on the crowns of trees, Acacia tortilis being the most popular species. Where the previous history was known, 44% of lappet-faced vulture nests were newly constructed, and the rest re-used from the previous year. The incubation period was about 55 days and the fledging period about 100 days in both species. Juveniles continued to frequent their nests after they could fly, sometimes for several months. Most lappet-faced vultures laid their eggs in April-May, the white-headed vultures in June-August. This means that the lappet-faced vultures raised their young during the dry season, when Grant's and Thomson's gazelles were the only animals present in any numbers on the plains. By contrast, the Ruppell's griffons nesting in the nearby Gol Escarpment colony raise their young during February-May, when the wildebeest and zebra herds are normally on the plains. The survival rate of lappet-faced vultures from laying to fledging was about 40%. The chicks are thought to be vulnerable to predation by tawny eagles, and one was known to have been killed by a leopard. Three adult vultures were killed on their nests, from unknown causes. Food remains from lappet-faced vulture nests showed a heavy preponderance of Grant's and Thomson's gazelles in all cases, with golden jackal the next most commonly occurring species. No food remains were obtained from white-headed vulture nests. The possibility of using aerial counts of vulture nests as an indicator of productivity is discussed.     

Re-use of courtship nests for quick remating in the polygynous Fan-tailed Warbler Cisticola juncidis

In a population of Fan-tailed Warblers Cisticola juncidis near Osaka, Japan, the males were polygynous, building a succession of elaborate courtship nests within their territories, and advertising them to females. Nest desertion by females frequently occurred early in the breeding cycle. Deserted nests were generally left untouched, but 17 out of 88 territorial males cleaned and re-used 20 of 79 nests deserted by females for their next courtship. The frequency of nest re-use increased with season. Of the re-used nests six (300%) were re-occupied by secondary females. Newly built nests were preferred to the 'second-hand' nests, probably because new nests were likely to last longer. Breeding success did not differ between the two categories of nests. In males, nest re-use seems to save time and energy expenditure for additional mating.     

Nest defence in the meadow pipit <Emphasis Type="Italic">Anthus pratensis</Emphasis>: the influence of renesting potential

The reproductive value hypothesis predicts that the level of nest defence is determined by the expected chance of offspring to survive until reproduction, and by the reproductive potential of the parents. Rates of survival from one breeding season to the next are low in small passerines, and their residual reproductive potential strongly declines as the current breeding season terminates. Therefore, we can expect that parents which have only one breeding attempt per season should defend their nests more intensively than parents with a possibility to renest. We studied nest defence in populations of meadow pipit (Anthus pratensis) breeding in Norway and the Czech Republic, differing in renesting potential. To simulate the threat from a predator, we placed a stuffed stoat (Mustela erminea) first 5 m and then 1 m away from a nest with nestlings. Parents increased or kept nest defence constant when the stoat approached their nests in Norway and, during a breeding season shortened by severe weather, in the Czech Republic (when renesting potential was limited). Parents decreased nest defence when the stoat approached the nest during “normal” breeding seasons in the Czech Republic (when renesting was common). These findings give support to the reproductive value hypothesis.     

Issue Information

The population of Yellow‐naped Amazons (Amazona auropalliata) declined by an estimated 50% between 1980 and 2000, and the current population is estimated to be between 10,000 and 50,000. Poaching of young has been a persistent problem, but the species is also threatened by habitat loss and degradation. Because most aspects of their life history, behavior, and ecology have not been examined in wild populations, we studied Yellow‐naped Amazons with the following objectives: (1) identify the species of trees used for nesting, (2) determine the size and potential function of breeding territories, (3) determine nesting success, and (4) examine their duetting behavior. We located nests at 16 sites on the Pacific Slope of Costa Rica from 1999 to 2008. We searched for nests from January to May. Every nest was visited at least once and some nests were visited every 2–3 weeks throughout the breeding season. We also collected territory and duetting data at one site (Ahogados). The breeding season of Yellow‐naped Amazons was during the dry season (January–May). Yellow‐naped Amazons nested in 21 species of trees, but 68% of nests were located in only five species, and cavities in dead coyols (Acrocomia aculeata) were used most often. We found no association between breeding success and the species of tree in which birds nested. Mean territory size was 25,578 m², and these small areas generally consisted of several trees surrounding a nest tree. Pairs continued to duet throughout the breeding season, suggesting that duetting is important for territory defense. The nest failure rate in our study was 89%, and most nest failures (64%) were due to poaching for the pet trade. We recommend immediate population management and conservation actions, including increased law enforcement to reduce nest poaching, protection of key nesting areas, educational programs, and habitat conservation.     

The effects of rainfall on different components of seasonal fecundity in a tropical forest passerine

Seasonal fecundity is a composite metric that is determined by component parameters such as clutch size, nest survival and re‐nesting probability. Many of these component parameters are known to vary with environmental conditions, in particular rainfall prior to or during the breeding season. In some species, seasonal fecundity is positively related to rainfall, but little is known about which component parameters of seasonal fecundity respond most strongly to rainfall. We used intensive nest monitoring of a multi‐brooded tropical forest passerine, the Montserrat Oriole Icterus oberi, to examine the effects of rainfall during the pre‐breeding season on component parameters of annual fecundity. We monitored all nests of a total of 42 pairs over 5 years in which rainfall varied substantially. We then related clutch size, nest survival, onset and length of the breeding season, re‐nesting probability and re‐nesting interval to pre‐breeding season rainfall using generalized linear mixed models that accounted for random variation across sites and individual pairs, and incorporated other variables known to affect the response. Higher pre‐breeding season rainfall led to an increase in clutch size and a decrease in re‐nesting interval, but nest survival, re‐nesting probability and length of the breeding season were not affected by variation in rainfall. The onset of the breeding season was delayed in very dry years. We conclude that higher rainfall is likely to increase food availability and thus body condition of female Montserrat Orioles, leading to an increase in fecundity due to larger clutch sizes.     

EDITORIAL

Olver, M. D. &; Kuyper, M. A. 1978. Breeding biology of the Whitebreasted Cormorant in Natal. Ostrich 49:25-30.

From 1972–1975 Whitebreasted Cormorants Phalacrocorax carbo bred at the Cedara Dam, Natal, South Africa (29 32S, 30 17E), and from 1973 they fished for food at Midmar Dam, 5 km away and carried the food back to the nestlings. Breeding occurred from April to October and was preceded by a period of courtship. Nesting material was collected by the males and the nests built by the females. The mean clutch size for 1972–1973 was 3,1. Both parents incubated the eggs and guarded the nest and chicks. Growth of the chicks was studied in 1972–1973. The mean number of chicks reared was 1,6 per nest although seven nests contained three nestlings. At 28 days they left the nest when alarmed, but could not fly until 49 days old. The average flying age appeared to be about 53 days. The height of the nests above the ground seemed to determine the nest leaving age. Of the 186 eggs laid in the 60 nests observed over two years, 74% hatched. Fledging success was 52% of eggs laid and 69% of eggs hatched. Chick mortality seemed to be caused mainly by falling from the nests and dying of starvation.     

Infestations of Ornithonyssus bursa,a haemotophagous mite,on starlings over the non-breeding season

Abstract

Ornithonyssus bursa (Berlese) (Dermanyssidae) is found in nests and neotboxes and on nestlings of the starling (Sturnus vulgaris L.), sometimes in large numbers, during the breeding season. During the non-breeding season the nestboxes and nest material are devoid of live mites. O. bursa overwinters ectoparasitically on starlings, and is present on approximately 25% of the population at the beginning of the breeding season. These nucleus populations build up rapidly in nest boxes during the breeding season.