Breeding biology of Orange‐breasted (Harpactes oreskios) and Red‐headed (H. erythrocephalus) trogons in Khao Yai National Park,Thailand

ABSTRACT As tropical habitats continue to be cleared or degraded, obtaining basic information about the ecology of birds in intact habitats is essential for understanding their life histories. We studied the breeding biology of Orange‐breasted Trogons (Harpactes oreskios) and Red‐headed Trogons (H. erythrocephalus) in Khao Yai National Park in Thailand from 2003 to 2009. Nests were in excavated cavities in well‐rotted stumps or other tree parts. Mean cavity heights were 2.1 m (N= 19) for Orange‐breasted Trogons and 2.0 m (N= 49) for Red‐headed Trogons. Eggs were laid every other day. For Orange‐breasted Trogons, the mean clutch size was 2.4 ± 0.1 (SE) eggs (N= 17); incubation periods for two nests were 17 and 18 d, respectively, and the nestling period ranged from 12 to at least 14 d (N= 4). For Red‐headed Trogons, the mean clutch size was 2.6 ± 0.1 eggs (N= 48), the mean incubation period was 18 d (N= 9), and the mean nestling period was 13.4 d (N= 5). In both species, both males and females excavated nest sites, incubated eggs, and brooded and provisioned nestlings. Only females incubated and brooded at night, and males provisioned nestlings more than females. Breeding seasons lasted from January to March for Orange‐breasted Trogons, and from late February to July for Red‐headed Trogons. Mayfield estimates of nest success were 8% and 9% for Orange‐breasted and Red‐headed trogons, respectively. Unusual for cavity nesters, nest failure due to predation was high and nestling periods short. The low nesting success is typical of many other tropical species, but considerably lower than reported for some Neotropical trogons, possibly due to the unenclosed structure of the nests of these Asian trogons.     

Behavior of adult and young grassland songbirds at fledging

The behavior of adults and young at the time of fledging is one of the least understood aspects of the breeding ecology of birds. Current hypotheses propose that fledging occurs either as a result of parent‐offspring conflict or nestling choice. We used video recordings to monitor the behavior of nestling and adult grassland songbirds at the time of fledging. We observed 525 nestlings from 166 nests of 15 bird species nesting in grasslands of Alberta, Canada, and Wisconsin, USA. Overall, 78% of nestlings used terrestrial locomotion for fledging and 22% used wing‐assisted locomotion. Species varied in propensity for using wing‐assisted locomotion when fledging, with nestling Grasshopper Sparrows (Ammodramus savannarum) and Henslow's Sparrows (Centronyx henslowii) often doing so (47% of fledgings) and nestling Song Sparrows (Melospiza melodia), Common Yellowthroats (Geothlypis trichas), and Chestnut‐collared Longspurs (Calcarius ornatus) rarely doing so (3.5% of fledgings). For 390 fledging events at 127 nests, camera placement allowed adults near nests to be observed. Of these, most young fledged (81.5%) when no adult was present at nests. Of 72 fledging events that occurred when an adult was either at or approaching a nest, 49 (68.1%) involved feeding. Of those 49 fledgings, 30 (62.1%) occurred when one or more nestlings jumped or ran from nests to be fed as an adult approached nests. The low probability of nestlings fledging while an adult was at nests, and the tendency of young to jump or run from nests when adults did approach nests with food minimize opportunities for parents to withhold food to motivate nestlings to fledge. These results suggest that the nestling choice hypothesis best explains fledging by nestlings of ground‐nesting grassland songbirds, and fledging results in families shifting from being place‐based to being mobile and spatially dispersed.     

Brood provisioning rates and fledgling behavior of Cordilleran Flycatchers in southwestern Colorado

The behavior of young songbirds after fledging is one of the least understood phases of the breeding cycle, although parental provisioning rates and movement of fledglings are key to understanding life history evolution. We studied Cordilleran Flycatchers (Empidonax occidentalis) at two sites in southwestern Colorado, USA, from 2012 to 2017. We banded and sexed breeding adults to determine the relative contributions of males and females to nestling and fledgling care, and attached radio‐transmitters to nestlings to facilitate observations of brood behavior after fledging. Females made 60% and 78% of total observed feedings of nestlings and fledglings, respectively. Parental provisioning rates increased with nestling age, and per‐nestling provisioning rates increased with brood size. Parental provisioning rates declined just before fledging, then increased just after fledging. Fledging times of individuals in broods were asynchronous and concentrated during the late afternoon and early evening. Males stopped caring for fledglings before females even though this species is single‐brooded, with some late‐season broods being abandoned by males. Broods spent the first three weeks after fledging within 400 m of nests, after which they began to disperse. Most aspects of the breeding biology of Cordilleran Flycatchers in our study, including the duration of nestling and fledging periods, female‐dominated provisioning, and movement patterns of fledglings, were similar to those of other Empidonax species. However, the times when young fledged were not concentrated in the morning as reported in most other songbirds, and this result warrants additional study of the timing of fledging in ecologically and taxonomically similar species. The increased per‐nestling provisioning rate with increasing brood size was unexpected, and additional study is needed to determine if this increase results from a trade‐off between adult annual survival and productivity favoring increased provisioning of young in larger broods, or from the existence of high‐quality individuals where larger clutches and higher provisioning rates are linked.     

Incubation temperature impacts nestling growth and survival in an open‐cup nesting passerine

For oviparous species such as birds, conditions experienced while in the egg can have long‐lasting effects on the individual. The impact of subtle changes in incubation temperature on nestling development, however, remains poorly understood, especially for open‐cup nesting species with altricial young. To investigate how incubation temperature affects nestling development and survival in such species, we artificially incubated American robin (Turdus migratorius) eggs at 36.1°C (“Low” treatment) and 37.8°C (“High” treatment). Chicks were fostered to same‐age nests upon hatching, and we measured mass, tarsus, and wing length of experimental nestlings and one randomly selected, naturally incubated (“Natural”), foster nest‐mate on days 7 and 10 posthatch. We found significant effects of incubation temperature on incubation duration, growth, and survival, in which experimentally incubated nestlings had shorter incubation periods (10.22, 11.50, and 11.95 days for High, Low, and Natural eggs, respectively), and nestlings from the Low treatment were smaller and had reduced survival compared to High and Natural nestlings. These results highlight the importance of incubation conditions during embryonic development for incubation duration, somatic development, and survival. Moreover, these findings indicate that differences in incubation temperature within the natural range of variation can have important carryover effects on growth and survival in species with altricial young.     

Behavioural responses to ectoparasites in pied flycatchers Ficedula hypoleuca: an experimental study

Nests of cavity‐nesting birds usually harbor some species of haematophagous ectoparasites that feed on the incubating adults and nestlings. Given the negative impact of ectoparasites on nestlings there will be selection on hosts to reduce parasite infestations through behavioural means. We have experimentally reduced the abundance of all ectoparasites in nests of pied flycatchers Ficedula hypoleuca to explore both whether there are changes in the frequency and duration of putative anti‐parasite behaviours by tending adults, as well as whether such anti‐parasite behaviours are able to compensate for the deleterious effects that parasites may have on nestlings. Heat treatment of nests substantially decreased the density of ectoparasites, and thereby positively affected nestling growth. The frequency and intensity of female grooming and nest sanitation behaviours during the incubation and nestling periods decreased as a consequence of the experimental reduction of ectoparasite infestation. Although nestlings begged more intensely in infested nests, the experiment had no significant effect on parental provisioning effort. Reduction of parasites resulted in larger nestlings shortly before fledging and increased fledging success. This study shows a clear effect of a complete natural nest ectoparasite fauna on parental behaviour at the nest and nestling growth in a cavity‐nesting bird. Although ectoparasites induce anti‐parasite behaviours in females, these behaviours are not able to fully remove parasite's deleterious effects on nestling growth and survival.     

Breeding biology and longevity of Russet-crowned Motmots in central Mexico

ABSTRACT.   Motmots, with their distinctive racketed-tails, represent one of the most easily recognized tropical birds, yet little is known about the basic natural history of most species in the family Momotidae. We report basic breeding biology and longevity of Russet-crowned Motmots ( Momotus mexicanus ), a medium-sized Neotropical bird that ranges from northwest Mexico to central Guatemala. We monitored nest success of eight pairs from 1 May to 17 July 1998 in tropical deciduous forests in central Mexico. Motmots laid an average of 4.1 eggs and incubated for approximately 20 d. Four of eight nests fledged young. Of these four nests, average hatching success was 69% and average fledgling success was 56%. The mean duration of the nestling period at three nests was 33.7 d. Based on the recapture of one individual bird in April 2008, we provide a longevity estimate that Russet-crowned Motmots can survive at least 11 yr in the wild. These data on nesting success and longevity add to our limited knowledge of the natural history of this understudied species.     

Breeding biology of the White-rumped Swallow Tachycineta leucorrhoa in Buenos Aires Province, Argentina

We conducted a study of the breeding biology of the White-rumped Swallow Tachycineta leucorrhoa nesting in nestboxes in a flat, farming landscape in Buenos Aires Province, Argentina. White-rumped Swallow nesting attempts were detected from the end of September to mid December, with most clutches laid during October. Birds laid clutches of 4–6 eggs with a mode of five eggs; most broods hatched synchronously (58%), but hatching spread could last up to 4 days. Nestling growth curves adjust well to logistic functions, and at day 15 nestlings attain the asymptotic weight of 21.6 g. Clutch size in White-rumped Swallows declined significantly as the season progressed. In addition, late-season eggs were smaller and late-season nestlings had a shorter nestling period and lower weight at day 15, probably leaving the nest lighter than early-season nestlings. These data suggest that the Swallows would benefit greatly from laying early in the season, which would provide nestlings with better survival prospects. However, both major sources of nest mortality, interspecific competition for nest-sites and nestling mortality during bad weather, decreased through the season. White-rumped Swallows follow the pattern found for other southern species, as it has smaller clutch size, lower growth rate and remains longer at the nest than its Northern Hemisphere congener the Tree Swallow Tachycineta bicolor .     

Importance of communal foraging grounds outside the reed marsh for breeding great reed warblers

Foraging habitat selection of breeding great reed warblers was studied at a shore of Lake Biwa. The foraging grounds of parent warblers during the nesting period were not restricted to the breeding territory of the reed marsh, their nestling habitat. The paddy field outside the reed marsh was used communally by them throughout the breeding season. Females with early stage nestlings did not visit the paddy field whereas when nestlings were older than 3 days, more than half of their total food was collected there. Females with nests adjacent to the paddy field tended to exploit the paddy field more often than those with nests distant from it. Monogamously mated females tended to exploit the paddy field more often than polygynously mated females. Food collected in the paddy field was larger than that in the reed marsh and parent birds were prepared to travel longer distances to exploit the rich source of food in the paddy field. The importance of the communal foraging ground outside the reed marsh as a background of the polygynous mating system of this species is discussed.     

Breeding biology of Eared Quetzals in the Sierra Madre Occidental, Mexico

ABSTRACT.   Eared Quetzals ( Euptilotis neoxenus ), a threatened species, are one of the least studied trogons in Mexico. We monitored 29 Eared Quetzal nests in the Chihuahuan portion of the Sierra Madre Occidental from 1998 to 2003. All nests were in tree cavities, and the mean tree and nest cavity heights ( N = 14) were 16.9 ± 7.8 m and 11.4 ± 4.1 m, respectively. The mean clutch size was 2.8 ± 0.9 eggs ( N = 28), the incubation period lasted 22 d ( N = 1), and nestling periods ranged from 29 to 31 d ( N = 5). Both adults incubated eggs and fed nestlings. Of 80 eggs, 70 hatched (87.5%) and 67 of 70 young fledged (95.7%). Twenty-five of 29 nests (86.2%) produced at least one fledgling. One nest was predated, and two failed when nest trees fell. Higher rates of nest predation have been reported for other species of trogons. However, fewer potential predators, such as snakes and mammals, are present in the Sierra Madre than in tropical zones where most trogon species occur. In addition, antipredator behaviors, including nestlings with calls resembling a snake and nests with an unpleasant odor, may contribute to the high nesting success. The main limiting factors for Eared Quetzals in the northern Chihuahua may be competition for cavities with other secondary cavity-nesters, and the failure of nests when snags fall.     

SOME NOTES ON THE SPOTTED FOREST THRUSH

Brown, C. J., Riekert, B. R. &; Morsbach R. J. 1987. The breeding biology of the African Scops owl. Ostrich 58: 58–64.

The incubation and nestling periods of two pairs of African Scops Owls Otus senegalensis breeding in nesting boxes in the Daan Viljoen Game Park near Windhoek were studied. The incubation and nesting periods were about 22 ± 2 days and 25–28 days respectively. Incubation and brooding was by the female. The male provided all the food during the incubation period, but by the end of the nestling period 30% of food was brought by the female. The growth of the nestlings, parental behaviour and foraging methods are describe2 Of 100 food items brought to the nests, 93% (by number) consisted of arthropods, 6% reptiles and 1% small mammals.     

Anti-social and social behaviour of adolescent yellow-rumped caciques (Icterinae: Cacicus cela)

In an individually marked population in southeastern Peru, males and females of the polygynous, colonial yellow-rumped cacique delayed successful breeding until they were 3 years old. Adolescent (2-year-old) females competed for nest sites, built nests, laid fertile eggs, incubated, and sometimes fed nestlings, but always abandoned nests before they fledged young. Females that completed nests during their adolescent years were also more successful in establishing nest sites the following year. Adolescent females that failed to establish nest sites and those that lost nests to predators tended to leave the study area altogether. By attempting to nest early, adolescent females may facilitate future nesting attempts by forming coalitions with other females and assessing nest site quality in an area. Adolescent males, on the other hand, avoided aggressive interactions with other males, but were very aggressive towards adult females and fledglings. Adolescent males attacked females in nests, chased females to and from the colony, pecked and mounted recent fledglings, and, rarely, pulled nestlings out of nests. This harassment resulted in the death of nestlings and fledglings and was energetically costly to females, which often fought adolescent males while defending their young. Adolescent males preferentially harassed nestling-feeding females, avoided egg-laying females and were never observed attempting to mate with females. Adult males rarely interfered during any of these interactions. Such anti-social behaviour may function as a way of practising adult behaviour, as a means of eliminating future competitors, or may be an epiphenomenon of rising hormone levels and therefore of no adaptive significance.     

The discovery of hatching and transition to feeding young by male Mountain Bluebirds

In many bird species, only females incubate the eggs, but both sexes feed nestlings. The means by which males of such species discover hatching and transition to feeding their offspring remains almost completely unexplored. Of particular interest are species with nests whose contents are concealed from view. During June and early July 2015 in the Bighorn Mountains of Wyoming, we used continuous video‐recording of nests of cavity‐nesting Mountain Bluebirds (Sialia currucoides) to document the transition to feeding young by males. We saw no evidence that females used distinct vocal or visual displays to signal hatching to males. Observing mates carrying eggshells away from, or food into, nest boxes did not appear to trigger provisioning by males. Rather, at all 24 nests observed, males did not begin feeding until they had come to nest boxes and presumably sensed the presence of hatchings directly. Individual males varied, however, in both the manner in which they inspected nest contents and the number of times they did so before starting to feed young. Although most males fully entered nest boxes where they could see, touch, hear, and possibly smell hatchlings (or eggshell parts), other males may have detected hatchlings only by sound or possibly smell while perched at a nest‐box entrance. Based on past studies of mice and doves, we suggest that, for provisioning behavior to begin, some kind of direct sensation of offspring may be necessary to activate relevant neurons in the medial preoptic area of the hypothalamus of males, an area of the brain important in parental care. Additional research is necessary to test this, and to examine the effects of factors such as hormone levels and breeding experience on the means and rapidity by which males discover hatching and transition to nestling provisioning.     

The Social System of a Communal Breeder,the Bay-winged Cowbird Molothrus badius

Molothrus badius (bay-winged cowbird), an icterine blackbird with cooperative breeding, shares behavioural and ecological characteristics with other communal nesters: it is sedentary, has a high annual survival rate (76.2%) and a strong nest-site tenacity (mean breeding dispersal of 41.9 and 89.4 m for males and females). Behavioural data, including collective agonistic displays, suggest group territoriality. Before egg hatching most breeders occurred as single pairs showing territorial behaviour (82% of nests), and nesting was usually solitary (distances to nearest nests of 25–103 m). Most breeders were apparently monogamous, with a 2.5% incidence of extrapair copulations in the territory during clutch formation. During the nestling stage one to four helpers occurred at 95% of M. badius nests. Most helpers were 1–2 years old, but older breeding adults (mostly males) that failed to rear their own offspring helped at the end of the season. The number of helpers increased (up to 4) with nestling age. Helpers were also recruited during the postfledging period, and group size reached up to 10 adults at this stage. Helpers mobbed predators and brood parasites, and provided 35% of the nestling food. Provisioning rate was positively and significantly correlated with number of helpers, although age of nestlings was the best predictor of overall food delivery rate. The helping system was almost obligate and productivity comparisons between nests with/without helpers are not possible. Data suggest that helpers increased the breeding success per nest. The correlation between the provisioning rates of parents and helpers was negative but non-significant. In 18% of nests 3 to 4 individuals were present before the nestling period, including cases of apparently polyandrous trios and one case of joint nesting by two pairs. Within Brown 's (1987) categories of social organization M. badius is mainly group territorial with plural nesting. Habitat requirements of M. badius are wide and nest sites do not appear to limit breeding. Kinship plays a role in the social system, as 9 of 12 helpers marked as nestlings helped their parents.     

Male parental care promotes early fledging in an open-nester, the Willow Warbler Phylloscopus trochilus

The importance of male parental care to female reproductive success was investigated in the monogamous Willow Warbler Phylloscopus trochilus by removing the male parent at two different stages of the breeding cycle. Females that were widowed at the start of egg-laying continued breeding and managed to raise their brood on their own with no apparent reductions in numbers fledged or fledgling body-mass. The widowed females compensated for the loss of male assistance by increasing their own food provisioning rate as compared with control females. However, widows spent less time brooding the small young, and the growth rate of nestlings was reduced. In nests where the male parent was removed 7 days after the eggs hatched, the subsequent growth rate of nestlings was still affected, which suggests that male care is influential throughout the nestling period. On average, broods reared by widows fledged 2 days later than did broods of control females. An extension of the nestling period may appreciably affect reproductive success, since 68% of nests failed due to predation, mostly during the nestling period. We suggest that the main role of male parental care in the Willow Warbler is to assure a high growth rate of nestlings, which leads to early fledging and hence a reduced risk of nest predation.     

Male rank, female breeding synchrony, and patterns of paternity in the boat-tailed grackle

Species in which males directly defend groups of breeding femalesoften have extreme skew in observed male mating success. Inonly a few species, however, has a corresponding skew in fertilizationsuccess been confirmed. Furthermore, the ecological and socialfactors contributing to variation in fertilization success needinvestigation. This study examined competition for mates andpaternity in the boat-tailed grackle (Quiscalus major). Observationsat colonies of nesting females revealed that the toprankingor alpha males performed more than 70% of the copulations. DNAfingerprinting indicated that alpha males sired less than 40%of nestlings. Nevertheless, analysis of band-sharing scoresamong nestlings from different nests suggested that alpha malessired more than three times as many offspring as any other individualmale. Because few nestlings were sired by the nonalpha malesthat associated with colonies, females must have mated withother males while on trips away from colonies. Analysis of paternitywithin broods revealed that at least half of all females hadtheir brood fertilized by more than one male. Alpha males' successat fertilizing eggs did not vary with the number of simultaneouslyreceptive females within a colony. Our results suggest that maleand female behavior in female-defense polygyny results fromcomplex coevolution of the sexes.     

The process of fledging in the Mountain Bluebird

Fledging is a critical event in the avian breeding cycle, but remains unstudied in almost all species. As a result, little is known about factors that cause nestlings to leave nests. We documented fledging behavior in a box‐nesting population of Mountain Bluebirds (Sialia currucoides) using radio‐frequency identification. We attached a passive integrated transponder (PIT tag) to the leg of each nestling in 40 nests. An antenna checked for the presence of a transponder signal (i.e., a nestling) at nest‐box entrances every 2 s. The time of last detection of a nestling was taken as the time that nestling fledged. We found that fledging began when the oldest nestlings were 15–22 d old. Broods that were ahead in development, as measured by primary feather length, fledged at relatively younger ages. All nestlings fledged on the same day at 33 nests (83%) and over 2 d at remaining nests. When all nestlings fledged on the same day, fledging usually began in the morning and median time between the first and last fledging was 55 min (range = 2.3 min–10.6 h). When young fledged over 2 d, fledging always began >8 h after sunrise and usually just one nestling fledged the first day, suggesting that this fledging may have been accidental. Clutches in our population often hatch asynchronously, which sets up a hierarchy within broods in developmental state, size, and competitive ability. In such situations, fledging may be initiated by one of the most‐developed and hence most‐competitive nestlings in a brood, presumably when it reaches a certain threshold state of development. Alternatively, fledging may begin when a less‐developed, less‐competitive, and probably hungrier nestling leaves the nest, presumably to gain better access to food. We used the proportion of time that a nestling was able to occupy the nest‐box entrance late in the nestling stage, waiting to intercept parents with food, as an index of nestling competitive ability. Assuming that the number of nest entrance detections reliably indicates nestling competitive ability, we found that the most‐competitive nestling fledged first at over half of all nests, supporting the notion that fledging usually begins when oldest nestlings reach a threshold state of development.     

Reproductive interactions of the Shiny Cowbird Molothrus bonariensis and the Yellow-hooded Blackbird Agelaius icterocephalus in Trinidad

The reproductive interactions of the Shiny Cowbird Molothrus bonariensis , a brood parasite, and the Yellow-hooded Blackbird Agelaius icterocephalus , a host of the cowbird, were studied In Trinidad, West Indies. We gathered information on the breeding biology of the Shiny Cowbird and the Yellow-hooded Blackbird, the frequency of use of the host species, and the effects of brood parasitism on host breeding success. Yellow-hooded Blackbirds are polygynous for the most part; males build nests and attempt to attract females to lay in them by means of song and visual displays directed towards the nests. This behaviour probably makes it easy for cowbirds to locate breeding birds and their nests. Cowbird eggs were found in 153 of 377 (40–3 %) blackbird nests located before the nestling stage. Shiny Cowbird parasitism of the Yellow-hooded Blackbird had little negative impact on host reproductive success, whereas predation accounted for the majority of nest failures. Vigilant nest defense by male blackbirds combined with colonial breeding apparently also minimized the extent of host egg damage and removal by cowbirds, and the parasitized and unparasitized nests were equally successful at producing blackbirds. Cowbirds most frequently parasitized the first or only nesting attempts in blackbird territories, and first or only nests were also successful more frequently than subsequent nests.     

Discrimination and ejection of eggs and nestlings by the fan-tailed gerygone from New Caledonia

Nestling rejection is a rare type of host defense against brood parasitism compared with egg rejection. Theoretically, host defenses at both egg and nestling stages could be based on similar underlying discrimination mechanisms but, due to the rarity of nestling rejector hosts, few studies have actually tested this hypothesis. We investigated egg and nestling discrimination by the fan-tailed gerygone Gerygone flavolateralis, a host that seemingly accepts nonmimetic eggs of its parasite, the shining bronze-cuckoo Chalcites lucidus, but ejects mimetic parasite nestlings. We introduced artificial eggs or nestlings and foreign gerygone nestlings in gerygone nests and compared begging calls of parasite and host nestlings. We found that the gerygone ejected artificial eggs only if their size was smaller than the parasite or host eggs. Ejection of artificial nestlings did not depend on whether their color matched that of the brood. The frequency of ejection increased during the course of the breeding season mirroring the increase in ejection frequency of parasite nestlings by the host. Cross-fostered gerygone nestlings were frequently ejected when lacking natal down and when introduced in the nest before hatching of the foster brood, but only occasionally when they did not match the color of the foster brood. Begging calls differed significantly between parasite and host nestlings throughout the nestling period. Our results suggest that the fan-tailed gerygone accepts eggs within the size range of gerygone and cuckoo eggs and that nestling discrimination is based on auditory and visual cues other than skin color. This highlights the importance of using a combined approach to study discrimination mechanisms of hosts.     

The social organization and breeding behaviour of the Yellow-faced Honeyeater Lichenostomus chrysops– a migratory passerine from the Southern Hemisphere

Southern Hemisphere passerines are generally thought to have long breeding seasons and high annual survivorship, but this may reflect a bias resulting from a disproportionate concentration on sedentary species. This study presents a detailed examination of the breeding biology and social organization of a migratory population of a passerine from the Southern Hemisphere – the Yellow‐faced Honeyeater Lichenostomus chrysops. It took place between 1997 and 2000 in the Coranderrk Reserve, Healesville, Australia. Following the birds’ return from migration, breeding commenced in mid‐November, roughly 2 months after arrival. The breeding season was short (3.5–4 months) compared with sedentary honeyeaters occupying the same habitat. Territories (0.19 ± 0.11 ha) were established by males but defended by both sexes against conspecific and heterospecific intruders. Within a breeding season, pairs were multibrooded (mean no. of clutches per season 2.14 ± 0.76, range 1–3) and always re‐nested within the same territory with the same partner. However, only 12.5% of pairs bred together in a subsequent breeding season despite, on many occasions, their partner from the previous season being alive (divorce rate of 75% for males and 66% for females). Females alone built the nest, incubated the eggs and brooded the nestlings. However, males contributed 44.5% of feeding visits to nestlings. The breeding cycle of Yellow‐faced Honeyeaters (clutch size 1–3 eggs, mean 2.4 ± 0.6, n = 84, incubation period 14.4 ± 0.7 days, n = 11, nestling period 13.0 ± 1.7 days, n = 6) was similar to that of sedentary honeyeaters (and Southern Hemisphere Corvidae in general), except that fledglings only remained on the parental territory for 2–3 weeks post‐fledging. At least one young fledged from 32.1% of nests (n = 156). Predation was the major cause of nest failure (74.5% of 106 failed nests). Only 4.4% of nestlings (n = 136) were observed on the study site in subsequent seasons (five males and one female). None of those males was observed on the study site until their second year of life. Adult annual survivorship (ignoring losses due to dispersal) was 43% for females and 51% for males. Our study suggests that if more data were available for the numerous migratory species from the Southern Hemisphere, some apparent differences from northern hemisphere passerines might disappear.     

Nesting biology of Eastern Yellow Wagtails at Cape Romanzof, Alaska

ABSTRACT.   The nesting biology of the Eastern Yellow Wagtail ( Motacilla tschutschensis ) was studied at Cape Romanzof, Alaska, an arctic tundra site on the Bering Sea coast near the northeastern limit of the breeding distribution of the Yellow Wagtail ( Motacilla flava/citreola/tschutschensis ) species complex. Ninety-four nests were located and monitored from 1996 to 1999. Females built nests in 5–7 d, and nests were located on the ground. The mean clutch size was 5.6 eggs, and the mean incubation period was 11 d. Both adults incubated, and some males had a partial brood patch. The mean duration of the nestling period was 11.6 d, and both parents brooded and fed the young. Some adults began the complete prebasic molt (including primaries) while their young were still in the nest. Nestling development was similar to that reported for other Yellow Wagtails ( sensu lato ), but the breeding cycle and breeding season of Eastern Yellow Wagtails was compressed relative to Western Yellow Wagtails in Europe and to other passerine species breeding in western Alaska. Some breeding events overlapped, including initiation of egg laying before completion of nest building and initiation of adult molt while young were still in the nest. Clutch sizes were larger than reported for most European relatives. Clutch size generally fit with models predicting an increase of about one egg per 19 degrees of increased latitude. Rapid nest initiation, overlap of breeding cycle events, nest attendance (including incubation) by males, and slightly larger clutches appear to be adaptations to high-latitude breeding in this long-distance migrant.