Survival Of Nestlings Research Articles

Multiple effects of brood parasitism reduce the reproductive success of prothonotary warblers, Protonotaria citrea

Avian brood parasitism often has multiple negative effects on the reproductive success of the host. Most studies have focused on one or two of these effects, but rarely have they all been studied simultaneously for one species. I studied prothonotary warblers to quantify the effects of different intensities of (i.e. multiple) brood parasitism by brown-headed cowbirds, Molothrus ater, on the production of host and cowbird young and on the between-year returns of adult warblers. Host clutch size decreased with an increase in the number of cowbird eggs laid in nests. The hatching success of warbler and cowbird eggs decreased with increased cowbird eggs in nests, but was always higher for cowbird eggs than warbler eggs. The survival of warbler nestlings, but not cowbird nestlings, decreased with increased cowbird nestlings in the brood. An increase in the number of cowbird nestlings in broods resulted in a reduction in the average mass of warbler nestlings but not cowbird nestlings. The number of cowbird eggs or nestlings present did not affect nest predation, and the fledging of cowbirds did not influence the renesting interval of female warblers. In addition, the between-year returns of adult warblers were not negatively affected by brood parasitism. Decreased hatching success and nestling survival reduced the reproductive output of the warblers the most. These effects were substantial and appear to favour the evolution of behavioural responses that reduce the effects of brood parasitism on prothonotary warblers. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour

Plasma corticosterone in American kestrel siblings: effects of age, hatching order, and hatching asynchrony

Although it is well documented that hatching asynchrony in birds can lead to competitive and developmental hierarchies, potentially greatly affecting growth and survival of nestlings, hatching asynchrony may also precipitate modulations in neuroendocrine development or function. Here we examine sibling variation in adrenocortical function in postnatally developing, asynchronously hatching American kestrels ( Falco sparverius) by measurements of baseline and stress-induced levels of corticosterone at ages 10, 16, 22, and 28 days posthatching. There was a significant effect of hatching order on both baseline and stress-induced corticosterone levels during development and these effects grew stronger through development. First-hatched chicks exhibited higher baseline levels than later-hatched chicks throughout development and higher stress-induced levels during the latter half of development. Furthermore, there was significant hatching span (difference in days between first- and last-hatched chicks) × hatching order interaction on both baseline and stress-induced corticosterone levels during development. Hatching span was also positively correlated with both measures of corticosterone and body mass in first-hatched chicks, but was negatively correlated with these factors through most of the development in last-hatched chicks. It is known that hatching asynchrony creates mass and size hierarchies within kestrel broods and we suggest that hierarchies in adrenocortical function among siblings may be one physiological mechanism by which these competitive hierarchies are maintained.

Yolk Testosterone Levels are Not Consistently Higher in the Eggs of Obligate Brood Parasites Than Their Hosts

Abstract The survival of obligate brood parasitic nestlings depends on their ability to exploit hosts' parental care, mostly at the expense of the unrelated nestmates. Foster parents are characteristically manipulated by parasitic young through more intensive begging displays. For example, young of parasitic brown-headed cowbirds (Molothrus ater) beg more loudly and elevate their head higher than the chicks of most host species. What is the developmental basis of this difference between parasite and its host species? Previous studies showed that intraspecific differences in some maternally deposited egg-yolk steroid hormone concentrations were related to differences in the begging behaviors and growth of hatchling birds. The prediction was tested that interspecific variation in yolk testosterone concentrations was related to consistent differences in the begging of hosts vs. parasites. Contrary to this prediction, yolk testosterone levels in the eggs of brown-headed cowbirds were not consistently higher t...

Spontaneous Micronuclei in the Black-Headed Gull (Larus RidibundusL.) Embryos in Relation to Parameters Determining Nestling Survival

The frequencies of spontaneous micronucleated erythrocytes were measured in the embryos of two distinct breeding populations of the Black-headed Gull. In total, 117 blood samples from the same number of Black-headed Gull embryos from Krivėnai colony and 97 blood samples from Kretuonas colony were examined. The influence of egg weight and volume, nest location within the colony, date of commencement of breeding and egg laying sequence in clutch on the levels of cytogenetic damage was evaluated. No statistically significant relationships have been established between spontaneous cytogenetic damage and qualitative parameters determining nestling survival till fledging and recruitment to the breeding population.

Parental Feeding Rates in the House Sparrow, Passer domesticus: Are Larger-Badged Males Better Fathers?

Elaborated secondary sexual characteristics may reflect genetic quality or good health, either of which may be associated with an individual's competence as a parent. We examined whether female house sparrows (Passer domesticus) paired to large vs. small-badged mates gain benefits in the form of increased parental care or improved nestling welfare. House sparrow nests where the male had been trapped and banded were observed for 1 h on at least 5 d during the peak growth period of nestlings. Male feeding shares, measured as the proportion of total feeds per chick made by the male, were marginally positively correlated with male badge size. Moreover, higher male shares of nestling feeding were associated with improved prospects for offspring survival, and a greater proportion of chicks fledged from the nests of larger-badged males. These results suggest that females paired to large-badged males gain direct benefits in the form of enhanced nestling survival, which presumably stem from factors associated with increases in the proportion of nestling feeding contributed by their mates.

Selection through predation, snowfall and microclimate on nest‐site preferences in the Water Pipit Anthus spinoletta

Nest‐site characteristics can have a strong impact on reproductive success in birds. Nest sites should simultaneously protect from predators, offer shelter and provide a favourable microclimate. We studied the relationship between three agents of natural selection (predators [i.e. Adders and birds/mammals], snowfall and microclimate), nest‐site characteristics and reproductive success to determine whether these influenced preference for specific nest‐site characteristics in the Water Pipit Anthus spinoletta. Pooled over all nests, the relative importance as agents of natural selection decreased from mammalian/avian predation (15% of all nests) through Adder predation (12%) to snowfall (7%), but there were clear differences in space and time. Predation by Adders selected for nest sites surrounded by few medium‐sized shrubs. Selection by mammalian and avian predators favoured no specific nest‐site characteristics. Protection from snowfall was best in nests surrounded by relatively few medium‐sized shrubs. Microclimate had a strong influence on nestling survival and duration of nestling period. In nests on ENE‐facing slopes, where maximum temperatures were reached in the morning, nestling survival was higher than on WSW‐facing slopes, where temperature maxima occurred in the afternoon. Our results indicate that weak, but significant, directional selection is acting on preference for certain nest‐site characteristics through effects on survival and development of nestlings. As predation and snowfall are unpredictable, the evolution of an optimal nest placement strategy is unlikely on a small scale. On a larger scale, however, choice of one breeding area over another may be favoured because of predictable differences between locations in terms of survival and nestling development.

Sex-biased initial eggs favours sons in the slightly size-dimorphic Scops owl (Otus scops)

We assessed the potential control of female Scops owls (Otus scops) over the production of daughters and sons in relation to their order in the laying sequence, and investigated the possible adaptive value of such control on the survival and growth of nestlings. The population sex ratio at fledging was not significantly biased. A relationship between ovulation order and egg sex was found, which was mostly due to the strong male biased sex ratio among initial eggs, as 17 of 18 first-hatched chicks (94%) from first-laid eggs were males. Asynchronous laying and subsequent asynchronous hatching resulted in a decreasing survival of chicks with increasing hatching order. Female chicks fledged with a higher mass than males and fledging mass decreased with hatching order due to male biased hatching order and its influence in the growth of the single first-hatched female. These results suggest that female Scops owls may be able to adjust the sex of their offspring at egg production to invest differentially in their survival and growth. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 76, 1–7.

Sex-biased initial eggs favours sons in the slightly size-dimorphic Scops owl (Otus scops)

We assessed the potential control of female Scops owls (Otus scops) over the production of daughters and sons in relation to their order in the laying sequence, and investigated the possible adaptive value of such control on the survival and growth of nestlings. The population sex ratio at fledging was not significantly biased. A relationship between ovulation order and egg sex was found, which was mostly due to the strong male biased sex ratio among initial eggs, as 17 of 18 first-hatched chicks (94%) from first-laid eggs were males. Asynchronous laying and subsequent asynchronous hatching resulted in a decreasing survival of chicks with increasing hatching order. Female chicks fledged with a higher mass than males and fledging mass decreased with hatching order due to male biased hatching order and its influence in the growth of the single first-hatched female. These results suggest that female Scops owls may be able to adjust the sex of their offspring at egg production to invest differentially in their survival and growth.

The State of Food Resources and Reproductive Success of Tufted and Horned Puffins in the Northern Sea of Okhotsk

Studies on the reproductive biology of seabirds on Talan and Umara islands in 1987–1999 showed that the diet of nestlings and reproductive success of the tufted puffin (Lunda cirrhata) and horned puffin (Fratercula corniculata) considerably varied in different colonies. This was determined by differences in the hydrologic characteristics of water areas and the state of food resources in Taui Bay (the northern Sea of Okhotsk). The reproductive success of tufted puffins was higher on Umara Island due to more favorable environmental conditions and relatively stable food resources in Odyan Bay. The parameters of reproductive success and the nestling diet in tufted and horned puffins from Talan Island differed considerably. The survival of nestlings was always higher in horned puffins, which was related to some characteristics of their feeding ecology.

Effects of predation and rabbit haemorrhagic disease on population dynamics of rabbits (Oryctolagus cuniculus) in North Canterbury, New Zealand

The impact of predation and rabbit haemorrhagic disease (RHD) on population dynamics of rabbits, and the survival of juvenile rabbits, was investigated between July 1999 and March 2000 in North Canterbury, New Zealand. Rabbit abundance and pre- and post-emergent rabbit mortality were monitored on four sites, two of which were subject to predator control. RHD spread naturally through all sites from late November to early December. Rabbit densities declined on all sites, but after the RHD epidemic, declines were significantly greater where populations of predators had not been controlled. Survival of rabbit nestlings was lower where predators were not controlled. All post-emergent radio-collared rabbits died at sites where predators were not controlled, whereas 18% of those collared at sites where predators were controlled survived to maturity. In contrast to the results from previous studies, rabbits born at the start of the breeding season had very high rates of post-emergent mortality, as they appeared to be susceptible to the RHD virus later in the breeding season. The age at which juvenile rabbits become susceptible to RHD, the timing of RHD epidemics, and the abundance of predators are likely to be important in determining survival of juvenile rabbits. This study demonstrates that predation can reduce rabbit populations to low levels, but only in combination with other factors, in this case RHD.

FACTORS ASSOCIATED WITH GROWTH OF NESTLING PROTHONOTARY WARBLERS

The Prothonotary Warbler (Protonotaria citrea) is the only wood warbler in the eastern United States that nests in cavities. It readily accepts nest boxes in lieu of natural breeding sites and therefore provides an excellent model for tests of ecological factors associated with reproductive success. During 1987, 300 nest boxes were placed along a 30-km transect along the tidal James River in eastern Virginia, and these nest boxes have been monitored every year through 2000. During the 1999 and 2000 breeding seasons, we collected 2910 measurements of nestling mass, and recorded ages of parental females, dates of clutch initiation and hatching, brood sizes, and the number of young that survived to fledging. Multivariate analysis of variance indicates that nestling mass was a significant function of brood size, hatching date, age of the female, and year, even when the effects of all independent variables were considered simultaneously. Growth rate and fledging mass were significantly lower in larger broods. Two- to three-year-old females fledged nestlings with greater mass than one-year-old females and females older than three years. Frequency of handling nestlings was not significantly associated with changes in their mass. Ambient temperature of the study area during the breeding season was significantly colder during 1999 than during 2000. Growth rate, fledging mass, and rate of survival of nestlings to fledging were lower during 1999 than during 2000. Growth of nestling birds was related to a large suite of intrinsic variables, but application of growth data to environmental concerns requires knowledge of both demographic and ecological factors.

Breeding occupancy and success of two hole‐nesting passerines: the impact of fragmentation caused by forestry

We studied the distribution and the reproductive success of the pied flycatcher Ficedula hypoleuca and the redstart Phoenieurus phoenicurus in relation to forest patch size, edge type (clearcut vs natural), distance from the forest edge, and vegetation characteristics in a forest‐dominated landscape. Breeding performances were recorded in up to 72 forest patches during 1992–1994 for birds breeding in nest‐boxes. In the spring, breeding individuals of both species arrived earlier in large forest patches (> 1 ha) than in smaller ones. Pied flycatchers arrived earlier on clearcut edges than natural edges but in the redstart there was no preference for a particular edge type. The territory distance from the forest to open land edge did not affect the arrival dates of either species. In the case of the pied flycatcher, the proportion of unpaired males was highest in patches < 1 ha in size and in the case of the redstart this applied to patches < 5 ha in size. Pairing success was not related to the forest edge type or the nest's distance from the edge. Nest predation was not patch‐size nor edge‐related for either of the species, but in the combined data for both species nest predation was higher at clearcut edges than at natural edges. Clutch size, brood size and the survival of nestlings to the fiedgling stage (fledgling/egg. %) were independent of the patch size, edge type and nest's “distance from the forest edge.

Activity Patterns and Effect of Ticks on Growth and Survival of Tropical Roseate Tern Nestlings

Activity Patterns and Effect of Ticks on Growth and Survival of Tropical Roseate Tern Nestlings

Activity Patterns and Effect of Ticks on Growth and Survival of Tropical Roseate Tern Nestlings

Abstract Patterns of abundance of the seabird tick Amblyomma loculosum and their effects on Roseate Tern (Sterna dougallii) nestling growth, fledging age, and survival are described on Aride Island, Seychelles, in 1997–1999. Female ticks attached to nestlings from 4 to 14 days (to engorge) whereas male ticks attached for 1–3 days. The linear growth rate of birds carrying female ticks (0.24 g/day) was significantly different from that of nonparasitized nestlings of the same age and similar (or even lower) hatching weight (4.07 g/day). Parasitized nestlings that fledged did so 5.2 days later than nonparasitized nestlings of similar age. Only 37.5% of the nestlings infested with female ticks fledged compared with 83.3% of the noninfested nestlings. During the successful 1998 breeding season, around 100 nestlings died from tick infestation (24.3% of the nestling deaths). Ticks appeared to accelerate nestling mortality during periods of food shortage. Despite an annual difference of two weeks in the timing of breeding of the Roseate Terns between 1997 and 1998, adult ticks parasitized nestlings in July, with an infestation peak occurring between 8–12 July in both years. However, in 1997, nestlings were parasitized at a younger age, suggesting that ticks (nymph stage) must attach to Roseate Tern adults as soon as they make a nest scrape (usually in May). Ironically, the frequent breeding failures of the Roseate Terns will result in lower infestation levels in subsequent years, which will benefit the birds.

Life on the edge: the demography of short‐season populations of deer mice

We documented populations of deer mice in the Kananaskis Valley, southwestern Alberta, Canada from 1979 to 1997 to determine whether these short‐season populations were more, or less, variable than populations in more temperate environments. We then examined patterns of reproduction, age‐specific survival, and immigration to explain variation in summer population growth. Population densities showed no multi‐annual periodicity and were generally low. At maximum, numbers doubled over the breeding season, but declined over the breeding season in 4 of 16 yr. Variability in population density was low, and similar to that of Peromyscus populations in more temperate environments. No demographic parameters were related to spring population densities, and immigration rates were low when conditions for survival of nestlings and adults were favorable. Variation in summer population growth was attributed primarily to variation in nestling survival among years.

On reproduction in lemmings

Many northern small mammals have restricted breeding seasons, which results in limited opportunities for reproduction by adults and delayed maturation until one year of age. Survival and longevity is enhanced under such conditions and the potential for population growth is low relative to small mammals in temperate environments. However, some northern small mammals, such as lemmings, are regarded as having high reproductive rates and a tremendous potential for population growth. Here I review what is known about lemming life histories. Available data indicates that lemmings have the potential for both summer and winter breeding seasons. During the summer, adults are generally restricted to only one or two litters during a short breeding season, and only the earliest-born young-of-the-year can mature in the summer of their birth. In most years, very few or no young mature in the summer of their birth, and in some years survival of nestlings is very poor. Survival to the winter breeding season is important for the persistence of populations under these conditions. Reproduction by lemmings in winter is poorly documented, but years with little or no winter breeding are not uncommon. Summers in which no young mature, or reproduction is unsuccessful, followed by winters in which no breeding occurs would favor lemmings that can successfully reproduce at an advanced age. A complete understanding of the role of age-specific reproduction in the dynamics of lemming populations awaits further study.

Diet and Postnatal Growth in Red-Legged and Black-Legged Kittiwakes: An Interspecies Cross-Fostering Experiment

AbstractRed-legged Kittiwakes (Rissa brevirostris) and Black-legged Kittiwakes (R. tridactyla) are morphologically similar, breed in mixed colonies, and nest at the same time, but they exhibit substantial differences in diet, rate of nestling provisioning, and foraging distribution. We cross-fostered nestlings of the two species to test the competing hypotheses that growth in mass of kittiwakes is constrained by diet (i.e. composition, provisioning rate, and quality) or by inherent species-specific physiology. Survival and body mass of cross-fostered nestlings at 30 to 32 days posthatching did not differ from those of conspecific controls. Black-legged Kittiwake fledglings had higher lean mass than Red-legged Kittiwake fledglings regardless of whether they were raised by foster or natural parents. However, nestlings of both species raised by Red-legged Kittiwakes were 50% fatter at 30 to 32 days posthatching than those raised by Black-legged Kittiwakes. Regurgitations from nestlings raised by Red-legged Kittiwakes consisted primarily of lanternfish and contained about twice the lipid (percent dry mass) as regurgitations from nestlings raised by Black-legged Kittiwakes. Consequently, growth rate of lean tissue was genetically and/or physiologically constrained, whereas rate of fat deposition was constrained by diet. We hypothesize that the adaptive significance of lanternfish in diets for Red-legged Kittiwake nestlings is manifest in higher prefledging and/or postfledging survival. Interspecific differences in energy density of food and food provisioning rates balanced each other so that rates of energy provisioning were similar.

Costs of Parasitism Incurred by Two Songbird Species and Their Quality as Cowbird Hosts

Abstract We measured the costs of Brown-headed Cowbird (Molothrus ater) parasitism incurred by Field Sparrows (Spizella pusilla) and Indigo Buntings (Passerina cyanea). We predicted that the frequent occurrence of nest desertion as a response to cowbird parasitism in Field Sparrows would be reflected by a higher cost of parasitism for that species. We also compared growth and survival of cowbird nestlings between hosts, predicting that they would do poorly at Field Sparrow nests because the latter appear to be avoided by cowbirds. Both species experienced reduced body mass gain in parasitized broods, but only Indigo Bunting suffered reduced tarsus growth. Both species experienced reductions in clutch size, hatching success, and nestling survival due to parasitism, but these losses did not differ among the two hosts. Multiple parasitism did not affect hatching success or nestling survival more than single parasitism for Indigo Buntings. Once accepted, cowbird offspring fared equally well in nests of both species, but almost half of all cowbird eggs laid in Field Sparrow nests were lost through nest abandonment. As parasitism costs to both species appear to be substantial, the rarity of nest desertion in Indigo Buntings may be due to other factors. Infrequent parasitism of Field Sparrows is consistent with host avoidance by cowbirds but other explanations should be explored.

COSTS OF PARASITISM INCURRED BY TWO SONGBIRD SPECIES AND THEIR QUALITY AS COWBIRD HOSTS

Abstract We measured the costs of Brown-headed Cowbird (Molothrus ater) parasitism incurred by Field Sparrows (Spizella pusilla) and Indigo Buntings (Passerina cyanea). We predicted that the frequent occurrence of nest desertion as a response to cowbird parasitism in Field Sparrows would be reflected by a higher cost of parasitism for that species. We also compared growth and survival of cowbird nestlings between hosts, predicting that they would do poorly at Field Sparrow nests because the latter appear to be avoided by cowbirds. Both species experienced reduced body mass gain in parasitized broods, but only Indigo Bunting suffered reduced tarsus growth. Both species experienced reductions in clutch size, hatching success, and nestling survival due to parasitism, but these losses did not differ among the two hosts. Multiple parasitism did not affect hatching success or nestling survival more than single parasitism for Indigo Buntings. Once accepted, cowbird offspring fared equally well in nests of both s...

DIET AND POSTNATAL GROWTH IN RED-LEGGED AND BLACK-LEGGED KITTIWAKES: AN INTERSPECIES CROSS-FOSTERING EXPERIMENT

Abstract Red-legged Kittiwakes (Rissa brevirostris) and Black-legged Kittiwakes (R. tridactyla) are morphologically similar, breed in mixed colonies, and nest at the same time, but they exhibit substantial differences in diet, rate of nestling provisioning, and foraging distribution. We cross-fostered nestlings of the two species to test the competing hypotheses that growth in mass of kittiwakes is constrained by diet (i.e. composition, provisioning rate, and quality) or by inherent species-specific physiology. Survival and body mass of cross-fostered nestlings at 30 to 32 days posthatching did not differ from those of conspecific controls. Black-legged Kittiwake fledglings had higher lean mass than Red-legged Kittiwake fledglings regardless of whether they were raised by foster or natural parents. However, nestlings of both species raised by Red-legged Kittiwakes were 50% fatter at 30 to 32 days posthatching than those raised by Black-legged Kittiwakes. Regurgitations from nestlings raised by Red-legged ...