Non‐breeding Cackling,Ross's and Snow Geese on Baffin Island show no loss of body mass during wing moult

Non‐breeding Cackling Branta hutchinsii, Ross's Anser rossii and Lesser Snow Geese Anser caerulescens caerulescens captured during remigial moult on Baffin Island in 2015 showed no loss of body mass with moult stage, and individual variation in mass was largely explained by sex and measures of body size (tarsus length). Exceptional conditions in 2015 resulted in almost no reproductive effort or success in that year, so captured geese of all three species were likely to have been non‐breeding individuals that initiated moult early, whereas there were almost no failed or successful breeders, which would normally moult later. This suggests that in a non‐breeding year (i.e. in the absence of competition from large numbers of goslings), locally moulting geese can obtain sufficient exogenous energy to meet their needs during the flightless wing moult period without losing body mass. This also is consistent with the hypothesis that in other species of geese, accumulation of fat stores prior to, and depletion of such stores during, wing moult is adaptive and likely to be a feature of individual plasticity to meet particular needs, such as undertaking moult migration to remote sites where precise foraging and predation conditions cannot be anticipated, or where competition from more dominant individuals may restrict their access to a reliable food supply.     

The benefit of large broods in barnacle geese: a study using natural and experimental manipulations

1. In precocial birds, where the young feed themselves, the costs and benefits of brood size are still poorly understood. An experimental manipulation of brood size was employed to examine the effects of brood size on both parents and young in a wild population of barnacle geese [ Branta leucopsis (Bechstein)] during brood-rearing on Svalbard.
2. Social dominance of the family unit, the amount of vigilance behaviour of the parents, the growth of the goslings in the family unit and an index of body condition for female parents during moult were all positively correlated with brood size.
3. When brood size changed as a result of natural events (i.e. predation or adoption) or experimental manipulation, rates of dominance, parental vigilance, gosling growth and female parent condition changed in a similar direction to the observed relation between the variable and brood size in unchanged broods.
4. After fledging, the fast-growing goslings in large broods survived better during autumn migration, while there was no apparent net cost in survival or next-year breeding for the parents.
5. Via a direct effect of brood size on dominance of the family unit, large broods were beneficial for both parent and young in a situation where there was strong intraspecific competition for the available food resources.
6. This study provides a clear demonstration of a causal relationship between brood size and various components of both gosling and adult fitness and is of direct relevance to the phenomenon of adoption and the evolution of brood size in this species.     

Resting metabolic rate in migratory and non‐migratory geese following range expansion: go south,go low

While many species suffer from human activities, some like geese benefit and may show range expansions. In some cases geese (partially) gave up migration and started breeding at wintering and stopover grounds. Range expansion may be facilitated and accompanied by physiological changes, especially when associated with changes in migratory behaviour. Interspecific comparisons found that migratory tendency is associated with a higher basal or resting metabolic rate (RMR). We compared RMR of individuals belonging to a migratory and a sedentary colony of barnacle geese Branta leucopsis. The migratory colony is situated in the traditional arctic breeding grounds (Russia), whereas the sedentary colony has recently been established in the now shared wintering area (the Netherlands). We measured RMR by oxygen consumption () during two ontogenetic phases (juvenile growth and adult wing moult). We also investigated juvenile growth rates and adult body mass dynamics. Mass‐independent was 13.6% lower in goslings from the sedentary colony than in goslings from the migratory colony. Similarly, in adult geese, mass‐independent was 15.5% lower in sedentary than in migratory conspecifics. Goslings in the Netherlands grew 36.2% slower than goslings in Russia, while we found no differences in body dimensions in adults. Adult geese from both colonies commenced wing moult with similar body stores, but whereas Russian barnacle geese maintained this level throughout moult, body stores in geese from the Netherlands fell, being 8.5% lower half‐way through the moult. We propose that the colony differences in resting metabolic rate, growth rate and body mass dynamics during moult can be explained by environmental and behavioural differences. The less stringent time constraints combined with poorer foraging opportunities allow for a smaller ‘metabolic machinery’ in non‐migratory geese. Our analysis suggests that range expansion may be associated with changes in physiology, especially when paired with changes in migratory tendency.     

NOTES ON THE PEARL-BREASTED SWALLOW HIRUNDO DIMIDIATA IN THE SOUTH-WESTERN CAPE

Earlé R. A. &; Herholdt, J. J. 1988. Breeding and moult of the Anteating Chat Myrmecocichla formicivora. Ostrich 59: 155–161.

The general breeding biology and moult of the Anteating Chat Myrmecocichla formicivora was studied in open grassveld over a two-year period. During the winter (July), groups were significantly smaller than during summer (December) (1,81 ± 0,50 versus 2,85 ± 1,35 birds per group). There was a large turnover of individuals in the study area but the total population stayed the same. The breeding season in the study area lasted from September to February but analysis of nest record cards from a larger area gave a breeding season of August-April. Two types of nests were used: 90,6% were burrows in sand banks or other excavations, but 9,4%were in the mud pellet nests of Greater Striped Swallows Hirundo cucullata (n = 53). Consecutive breeding attempts were never made in the same burrow. Clutches consisted of three, four or five eggs ([Xbar] = 3,73 ± 0,67). Incubation lasted 14–14,5-15 days. The nestling period lasted 15–18 days. Fledgling/egg breeding success was 41,8% with 48,2% of all eggs not reaching the hatching stage. Juveniles showed an unequal sex ratio of 0,57 ♂ ♂: 1,0 ♀ ♀ but adults had a nearly equal ratio (0,9 ♂ ♂: 1,0 ♀ ♀). There was a significant positive correlation between the primary moult score and the week of the seven months in which moult was recorded. Juveniles underwent a complete body moult and partial primary moult 3–4 months after fledging.     

Factors affecting escape behaviour in moulting Greylag Geese Anser anser

The escape behaviour of flightless greylag geese Anser anser has been studied at a Danish moult site. In more than 40% of escapes, a stimulus could not be discerned, suggesting some importance of inaccurate risk assessment among the geese. Quasi-predator stimuli, for example gull alarms and helicopters, were also important and caused 31–43 and 5–13% of escapes, respectively. Geese were, however, displaced in less than 5% of encounters with these stimuli. Each escape prevented geese from feeding for 19 min on average, and hence, the cost of escapes was high. This, the low in-situ predation risk, and the partly distant and not directly threatening nature of the stimuli may have weakened the response of the geese. During the main moult period the geese were, nevertheless, more susceptible to quasi-predator stimuli than before moult—the probability of escape per 15 min period was 0.16–0.22 during moult and 0 before moult. The probability of escapes among moulting geese, which formed large cohesive flocks, was, furthermore, significantly enhanced with increasing flock size. It is possible large flocks were better at detecting quasi-predator stimuli, or simply that there was a greater risk of signals from flock members being misinterpreted. Thus in terms of maintaining uninterrupted foraging it was concluded that an individual would incur extra cost by joining large flocks during the moult period.     

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.     

Breeding ecology of the Clay-coloured Robin Turdus grayi in lowland Panama

The breeding ecology of Clay-coloured Robins Turdus grayi was studied in 1979 in the former Canal Zone of lowland Panama. Two study areas were chosen close together, Summit Gardens (27-3 ha), an ecological island of habitat suitable for Clay-coloured Robin surrounded by forest, and Morgan's Gardens (3–6 ha), a similar island surrounded by deforested areas and settlements. Eighty-three active nests were found and checked. The breeding season lasted from 2 March to 21 June. In Morgan's Gardens the first broods were raised in the dry season and second broods in the rainy season; in Summit Gardens most broods started at the beginning of the rainy season. In comparison to the closely related Blackbird T. merula in Poland, Clay-coloured Robins build nests on isolated trees or bushes, usually in more conspicuous sites (interpreted as an anti-predator adaptation) and on flexible, horizontal branches off the main trunk. Over 45% of broods were destroyed by predators but other factors causing brood loss were negligible. Nests built on palms were considerably safer. In the dry season the predation rate was low (5%) and increased during the course of the rainy season. Unlike Blackbirds, Clay-coloured Robin nestlings were given a lot of fruit; their diet was diversified. Starvation occurred in 60% of nests although usually only the youngest nestling died. Breeding density in Morgan's Gardens at 50 pairs per 10 ha was much higher than in Summit Gardens at 15>8 pairs per 10 ha. Breeding losses were lower, the nestlings were fed more fruit, the average nestling weight was lower and the production of fledglings per breeding pair was twice as high in Morgan's Gardens. It was concluded that a strategy of settling in a rather overpopulated place with hard foraging conditions but lower predation was better than settling in a area with a better food supply but higher predation.     

Habitat exploitation and interspecific competition of moulting geese in East Greenland

Jameson Land, East Greenland is a moulting area of c. 5000 non-breeding Pink-footed Geese and 5000 Barnacle Geese. Breeding populations of both species in the area are small and scattered. The moulting Pinkfeet originate from Iceland, and the Barnacle Geese from other parts of East Greenland. Both species arrive in the area at the end of June and moult their remiges in July. Moulting flocks of the two species seldom mix. Pinkfoot flocks are common along coastlines, in wide rivers and on lakes with open views to all sides, while Barnacle Geese predominate in smaller rivers and on lakes with surrounding hills. During moult the geese, and especially the Pinkfeet, are extremely wary and depend on a safe area of water serving as a refuge with nearby food supplies (sedge-dominated marshes). Barnacle Geese graze in a zone 0–100 m from the refuge, Pinkfeet up to 200–250 m from the refuge. The moulting sites fill up with geese according to available marsh areas, and the grazing pressure on average amounts to 594 goose-days per ha during the moulting period. Food intake is estimated at 149 g and 138 g organic material per 24 h by Pinkfeet and Barnacle Geese, respectively, [n 1984, which was sunny and warm, net above-ground primary production of a Carex subspathacea marsh (the prime feeding ground during moult) from the beginning of growth to the end of July was 13–15 g dw m², and it is estimated that the geese consumed 60–69% of the production. In 1983, which was cold, geese probably consumed the entire production. Goose grazing did not affect productivity, but nutrient levels were high in grazed compared with ungrazed shoots, and peaked in early July. When separate, the diet of both species comprises sedges and grasses. Where the species co-exist the amount of mosses in the diet increases, especially in Barnacle Geese. With respect to nutrient and fibre contents, moss is a suboptimal food compared to sedges and grasses. When separate, the geese spend 41–46% of the 24 hr grazing. Where they co-exist, Barnacle Geese spend 62% of the time grazing, while Pinkfeet seem unaffected by the presence of Barnacle Geese. It is argued that carrying capacity for moulting geese is reached. Geese compete for resources, the Barnacle Goose suffering from the presence of the other. The observed distribution pattern is suggested to result from (1) Pinkfeet being limited to certain sites due to extreme wariness, and (2) Barnacle Geese trying to avoid competition by utilizing sites which Pinkfeet are reluctant to use. The experience of older Barnacle Geese of stress when settling with Pinkfeet may be the segregation mechanism. Moult coincides with the onset of growth and peak nutrient levels in the vegetation. It is suggested that the geese undertake moult migrations to Jameson Land both to avoid competition for resources with breeding geese and because they gain advantage from a growing, nutritious vegetation.     

FACTORS AFFECTING EGG-WEIGHT, BODY-WEIGHT AND MOULT OF THE WOODPIGEON COLUMBA PALUMBUS

The heaviest clutches (2 eggs) laid by Woodpigeons Columba palumbus in a Cambridgeshire study area weighed 30% more than the lightest. Yet the variation in egg-weight within clutches was less than 1 %. Irrespective of initial weight, eggs lost weight at the same constant rate during incubation. Heavy eggs hatched more successfully than light eggs and none weighing less than 16 g hatched. There was no correlation between chicks' weight at hatching and their weight at day 6 during the July-September part of the breeding season. The ability to feed crop milk at this stage could compensate for low chick-weight, but this might not be true early in the season. Weight at day 6 was correlated with the weight at day 16 or 17. The growth pattern is discussed. Chicks in broods of one achieved a higher weight at day 17 than those in broods of two. The survival rate both in and after leaving the nest was the same in both brood-sizes. Chick-weight in artificially created broods of three was almost as high as in broods of two, but again data refer to the July-September period when abundant cereal food is available. Survival before and after fledging was lower in broods of three. Clutch- and egg-weight declined from April until September. It is suggested that this is adaptive, in that the adults produce heavier eggs when food supplies are most difficult to collect. The critical period probably occurs during the few days when the adult must produce crop milk and the young cannot be left unattended. Thus egg-weight depends on the female's capacity to acquire nutrients, and is related to the needs of embryonic development and the amount of compensation in nutrient supply which can be provided immediately after hatching. But clutch-size is more related to the bird's ability to feed and rear young to the point of fledging, thereby influencing the number of offspring which survive to leave progeny. Egg-weight and female body-weight were positively correlated in females weighing less than 480 g but not in heavier females. First-year birds did not acquire adult weight until midsummer and they would probably produce light eggs if they could breed before this month. However, their gonads do not recrudesce until July and this prevents them breeding in the spring. Seasonal changes in body-weight and fat content of adults and first-year birds are described and discussed; differences were noted between adult males and females which were considered to be adaptive. The moult is described. It begins in April and continues until November, approximately one pair of primaries being replaced per month. The moult ceases during the winter months, when it is known that food supplies become limiting. Woodpigeons lay light eggs relative to their body-weight but can achieve the extra parental care needed for the altricial chicks by producing crop milk. Because the moult is extended, the energy demands of moulting and breeding combined are relatively low and this enables the Woodpigeon to have a long breeding season and to moult coincidentally.     

Effects of food variability on growth rates, fledging sizes and reproductive success in the Yellow-eyed Penguin Megadyptes antipodes

Effects of a change of diet on growth rates and fledging sizes of Yellow-eyed Penguins Megadyptes antipodes were examined at two breeding areas on South Island, New Zealand, during two breeding seasons. An adverse change in diet was observed in the second season. Evidence for this included depressed growth rates of weight, differential growth of weight and most morphometric parameters between one- and two-chick nests in the second season, lower fledging weights, lower adult body weights, delayed moult, higher chick mortality and higher adult mortality during moult. The change in diet is suggested as being from one including oil-rich prey species, to one of oil-poor species.
Growth rates of first- and second-hatched chicks, and of survivors and non-survivors within a brood were not significantly different in either season, and growth rates of two-chick broods were only slightly slower than one-chick broods for some parameters in the second season. This, and synchronous hatching of chicks, equal egg-size and lack of sibling competition during feeding sessions, suggests that brood reduction is not an option available to Yellow-eyed Penguins, and that food supply may not be a limiting factor in the majority of breeding seasons.
Few changes in growth rates of morphometric parameters at either breeding area, and similar absolute sizes at fledging, indicate that slowing of growth rates of morphometric parameters only occurs when feeding conditions are so bad as to result in mortality and that, although fledging periods may be longer, patterns of development remain essentially unchanged.     

Moult migration of emperor geese Chen canagica between Alaska and Russia

We studied reproductive success and post-breeding movements of 32 adult female emperor geese Chen canagica that were marked with satellite radio transmitters on their nesting area on the Yukon-Kuskokwim Delta (YKD), Alaska 2000–2004. All 16 females that failed to successfully reproduce departed the YKD and moulted remiges either on the north coast of the Chukotka Peninsula, Russia (n=15), or on St. Lawrence Island, Alaska (n=1). Of 16 females that successfully nested, one migrated to Russia following hatch whereas the remainder stayed on the YKD. While moulting on the Chukotka Peninsula, emperor geese with satellite transmitters primarily used coastal lagoons west of Kolyuchin Bay. We observed 21,150 adult-plumaged emperor geese during aerial surveys in Chukotka in 2002. Most (95%) were in the same region used by geese that had been marked with satellite transmitters in Alaska. The number of emperor geese observed in Russia was comparable to our estimate of ≥20,000 adults that either do not nest or nest unsuccessfully each year on the YKD, suggesting that most nonproductive adults, or ≥28% of the adult population departs the YKD to moult elsewhere. The number of moult migrants may be substantially higher in years of poor reproductive success or if adult-plumaged birds that are not of breeding age also leave the YKD. Moult migration of emperor geese between Alaska and Russia is likely substantially greater than previously believed. Russian moulting habitats are important to the North American population of emperor geese and events that affect survival of geese in Russia could impact population trends on the YKD. Protection of coastal lagoons on the north coast of Chukotka is warranted.     

Keeping up with early springs: rapid range expansion in an avian herbivore incurs a mismatch between reproductive timing and food supply

Within three decades, the barnacle goose population wintering on the European mainland has dramatically increased in numbers and extended its breeding range. The expansion has occurred both within the Arctic as well as by the colonization of temperate areas. Studies of performance of individuals in expanding populations provide information on how well species can adapt to novel environments and global warming. We, therefore, studied the availability of high quality food as well as timing of reproduction, wing moult, fledgling production and postfledging survival of individually marked geese in three recently established populations: one Arctic (Barents Sea) and two temperate (Baltic, North Sea). In the Barents Sea population, timing of hatching was synchronized with the peak in food availability and there was strong stabilizing selection. Although birds in the Baltic and North Sea populations bred 6–7 weeks earlier than Arctic birds, timing of hatching was late in relation to the peak in food availability, and there was moderate to strong directional selection for early breeding. In the Baltic, absolute timing of egg laying advanced considerably over the 20‐year study period, but advanced little relative to spring phenology, and directional selection on lay date increased over time. Wing moult of adults started only 2–4 weeks earlier in the temperate populations than in the Arctic. Synchronization between fledging of young and end of wing moult decreased in the temperate populations. Arctic‐breeding geese may gradually accumulate body stores from the food they encounter during spring migration, which allows them to breed relatively early and their young to use the peak of the Arctic food resources. By contrast, temperate‐breeding birds are not able to acquire adequate body stores from local resources early enough, that is before the quality of food for their young starts to decrease. When global temperatures continue to rise, Arctic‐breeding barnacle geese might encounter similar problems.     

A comparison of breeding and moult cycles and life histories in two tropical starling species: the Blue-eared Glossy Starling Lamprotornis chalybaeus and Rüppell's Long-tailed Glossy Starling L. purpuropterus

The Blue-eared Glossy Starling Lamprotornis chalybaeus and Rüppell's Long-tailed Glossy Starling Lamprotornis purpuropterus were investigated in the field and in aviaries at Lake Nakuru National Park, Kenya for seasonality in reproductive activity and moult. The former species was found to be a seasonal breeder which nests after the onset of the heavy rains in April. Although some birds had large gonads prior to the rains in the dry season no nesting occurred. The rains were contemporary with increases in gonadal size and the plasma titres of LH, testosterone (T) in males and estradiol (E2) in females. These hormones are associated with the initiation of breeding activity. As breeding ceased in July and the moult began, the plasma titres again decreased. There was a bimodal breeding pattern which paralleled a change in biotope preference for nesting. Early nests, in the heavy rains, were on the open savanna and later nests were in the acacia forest. Late nesting birds also had delayed peaks in gonadal size, plasma titres of LH, T and E2 and a delayed moult onset. Data on individual captive birds demonstrate that these annual cycles have a distinctly individual character superimposed on the seasonal trends. In Rüppell's Long-tailed Glossy Starlings no seasonality in breeding was found although the flight feather moult commenced and was completed in all individuals at about the same time. The moult extended over about ten months, so a great deal of breeding-moult overlap was present. The absence of seasonality in field birds was reflected in the aviary birds, which had no pronounced cycles in the reproductive parameters measured (gonadal size, LH, T and E2 plasma titres). Breeding in field birds was regulated on a pair basis and correlated with increases in duetting. The striking differences in the seasonal organization between this species and Blue-eared Glossy Starlings were presumably due to the different biotope preferences and social behaviour of the two species.     

Predation by sparrowhawks favours early breeding and small broods in great tits

The selective pressures determining timing of reproduction and brood or litter size in animals remain to be clarified, despite much research. In several detailed studies of birds, selection for an early start of breeding has been demonstrated. Young born early in the season are often assumed to benefit from long experience, high dominance in flocks and/or early settlement in territories. For forest-breeding great tits (Parus major) in Sweden, predation by sparrowhawks (Accipiter nisus) was lower on fledglings hatched early than on those hatched late in the season. Hawk predation may therefore contribute to the higher success of early breeding great tits. Factors favouring early fledglings were (1) increasing food demands over the season in breeding hawks, and (2) hunting by hawks mainly in non-forest habitats when early tit fledglings left their nests. The proportion of fledglings taken was lower in broods of 2-6 than in broods of 7-12, indicating that predation favours small broods. Fledglings in large broods may be more vulnerable due to (1) a higher level of hunger and begging, and (2) higher provisioning rates by parents, which may reveal sites with fledglings to hawks. Territories of sparrowhawks were used as sample units in the statistical analysis, leading to strong inferences about predation at the landscape level.     

Increased nest predation in a declining and threatened Temminck's Stint Calidris temminckii population

We measured nesting success of the Temminck's Stint Calidris temminckii along the Finnish Bothnian Bay coast during 19 breeding seasons (1983–2001) and conducted a population census (1999–2002). We found 105 pairs, showing a marked decline from the previous survey (170 pairs 1987–95). Of the 424 'known-fate' nests, 47% hatched. Depredation caused 79.9% of the nest losses. Nesting failures increased from 1983–91 to 1992–2001 owing to a rise in nest predation. The proportion of failed nests that failed because of predation rose from 48.9 to 87.7%. When only depredated nests were considered as losses, Mayfield nest survival probability over the incubation period dropped from 69 to 31% (461 nests). This pattern emerged both in man-made and in natural habitats. Survival probability was independent of habitat type (natural vs. man-made). In an experiment involving videotaping of dummy nests, Common Gull Larus canus and Ruddy Turnstone Arenaria interpres were found to be the most important egg predators.     

Constrained by available raptor hosts and islands: density-dependent reproductive success in red-breasted geese

In this paper we aim to explain the distribution of red-breasted geese Branta ruficollis over different nesting habitats. To be safe from land predators red-breasted goose colonies were restricted to i) islands on rivers, ii) cliffs with peregrine falcons Falco peregrinus , and iii) the close proximity of snowy owl Nyctea scandiaca and rough-legged buzzard Buteo lagopus nests. Among years nest site availability varied by fluctuations in numbers of owls and buzzards in association with cycles in lemming abundance, but the total number of goose nests found in the study area did not vary. The distribution of geese, in combination with data on reproductive success, suggested a despotic mechanism: at cliffs, goose numbers were constant among years with an invariably high reproductive success, whereas large fluctuations in numbers on islands coincided with opposite trends in success. Apparently, geese nesting with owls or buzzards moved to the few islands present in the study area during years when these birds of prey were absent. Consequently, in such years the average density of geese on islands was more than twice as high as at cliff colonies (5.4 and 2.3 pairs per ha of foraging habitat, respectively). Colony size at cliffs may have been restricted by territorial behaviour of the geese, though there is evidence that, additionally, the host falcons also limited the number of nesting geese. Apparently rare in closely related species, we observed a negative density-dependent effect on reproductive success during the nest phase, and attribute this to limited food resources, reinforced by the high frequency of territorial interactions. This leads to the conclusion that, in addition to predation pressure, nesting density is an important agent in the link between lemming cycles and goose breeding success.     

Direct and indirect effects of an insect outbreak increase the reproductive output for an avian insectivore and nest‐cavity excavator,the red‐breasted nuthatch Sitta canadensis

Community‐wide food pulses may ameliorate food constraints but may also result in increased competition for other resources and predation rates. In cavity‐nesting vertebrate communities, where the availability of tree cavities can limit reproduction and the reuse of cavities can increase nest predation by squirrels, excavators may maximize their fecundity by creating new cavities in competitor‐ and predator‐rich habitats that undergo food pulses. The reproductive cost associated with excavation (i.e. increased energy allocation early in the breeding season that often delays laying and thereby reduces clutch size), may be reduced if food pulses allow for a longer breeding season and larger clutches. A large‐scale mountain pine beetle Dendroctonus ponderosae outbreak that occurred during our long‐term study (1995–2009) provided a natural food supplementation experiment across 27 sites in British Columbia, Canada. We examined the effects of a reduction in food constraints accompanied with increases in excavation rates, conspecific density and nest predation risk on the fecundity of a facultative excavator, the red‐breasted nuthatch Sitta canadensis. We found a total of 420 nests in tree cavities. Nuthatch clutch sizes ranged from two to nine eggs, and broods from one to nine fledglings per nest. Later clutches were larger at sites and in years with high beetle abundance (mean clutch size of six eggs did not decline later in the season), second broods were produced in outbreak years (usually only one nesting attempt/normal year), and the number of fledglings per successful nest increased with increasing beetle abundance and nuthatch densities, but declined with increased squirrel densities. Since fecundity did not differ between new and reused cavities, the costs and benefits of excavation versus cavity reuse may be neutralized for nuthatches during strong resource pulses. Overall, the beetle outbreak reduced food constraints for nuthatches and provided alternate food for nest predators, allowing increased annual fecundity.     

Movements and Survival of Molt Migrant Canada Geese From Southern Michigan

ABSTRACT We studied movements and survival of 250 female giant Canada geese (Branta canadensis maxima) marked during incubation with either satellite-monitored platform transmitting terminals or very high frequency radiotransmitters at 27 capture areas in southern Michigan, USA, in 2000–2003. We destroyed nests of 168 radiomarked females by removing eggs after day 14 of incubation, and we left nests of 82 incubating hens undisturbed after capture and marking. Of females whose nests we experimentally destroyed, 80% subsequently migrated from breeding areas to molt remiges in Canada. Among 82 nests left undisturbed, 37 failed due to natural causes and 51% of those females departed. Migration incidence of birds that nested in urban parks was low (23%) compared with migration incidence of birds that nested in other classes of land use (87%). Departure of females from their breeding areas began during the second and third weeks of May, and most females departed during the last week of May and first week of June. Based on apparent molting locations of 227 marked geese, birds either made long-distance migratory movements >900 km, between latitudes 51° and 64° N, or they remained on breeding areas. Molting locations for 132 migratory geese indicated 4 primary destinations in Canada: Western Ungava Peninsula and offshore islands, Cape Henrietta Maria, Northeast James Bay and offshore islands, and Belcher Islands, Hudson Bay, Canada. Following molt of remiges, Canada geese began to return to their former nesting areas from 20 August through 3 September, with 37% arriving on or before 15 September and 75% arriving on or before 1 October. Migration routes of geese returning to spring breeding areas were relatively indirect compared with direct routes taken to molting sites. Although overall survival from May through November was 0.81 (95% CI: 0.74–0.88), survival of migratory geese marked on breeding sites where birds could be hunted was low (0.60; 95% CI: 0.42–0.75) compared with high survival of birds that remained resident where hunting was restricted (0.93; 95% CI: 0.84–0.97). Nest destruction can induce molt migration, increase hunting mortality of geese returning from molting areas, and reduce human-goose conflicts, but managers also should consider potential impacts of increasing numbers of molt migrants on populations of subarctic nesting Canada geese.     

Optimal brood size and its limiting factors in the Rufous Turtle DoveStreptopelia orientalis

Optimal brood size and its limiting factors of the Rufous Turtle Dove,Streptopelia orientalis, were studied at the campus of the University of Tsukuba, Japan, during the breeding season in 1990–92. The dove usually lays two eggs in a nest. I made nests of a brood size of one and three by transferring a hatchling from one nest to the other, and compared their fledging success, factors of breeding failure, weight and tarsus length at fledging, growth rate and nestling period with those of a brood of two. The index of fitness (fledgling weight multiplied by average number of fledglings per nest) was almost the same in broods of two and three. However, the highest variation in fledging weight within the brood and the extension of nestling period were observed in broods of three, which caused the extension of inter-brood interval and consequently the smaller number of broods in the total breeding season. Therefore, broods of three would not have an advantage in producing more offspring than broods of two. Crop milk production had an effect on the growth of nestlings in the early phase of the nestling period, but the rapid growth in the granivorous phase compensated for the growth delay of the smallest nestling in broods of three. Small brood size and a large number of broods in a season would also be more effective under high predation pressure.