Chick Age Research Articles

Variation in faecal corticosterone metabolites in an Arctic seabird, the Little Auk (Alle alle) during the nesting period

Glucocorticoids participate in the control of whole body homoeostasis and an organism’s response to stress. Corticosterone, which is the principal glucocorticoid in birds, has been shown to increase in response to different energetic demands and perturbations that individuals have to cope with. In this study, a non-invasive method to examine the corticosterone secretion by measuring faecal corticosterone metabolites (FCM) has been established for an Arctic seabird, the Little Auk (Alle alle). A group-specific immunoassay was successfully validated for adults and chicks using an adrenocorticotropic challenge test. Then, FCM levels were investigated under different energetic and physiological demands, determined by weather conditions, week of chick rearing in adults, and age in chicks. The amount of rainfall had no effect on FCM levels in adults, whereas it negatively affected FCM levels in chicks. There was no variation in FCM concentrations among weeks of chick rearing in adults. In chicks, the FCM levels increased with age. Moreover, chicks with higher FCM levels had lower body mass and fledged later than chicks with lower FCM levels. This study demonstrates that environmental stress such as poor weather conditions can trigger significant changes in corticosterone levels in seabird chicks. Furthermore, the results indicate that corticosterone may be involved in the physiological and behavioural adjustments necessary for successful fledging and post-fledging survival.

Calculation of crystalline lens power in chickens with a customized version of Bennett’s equation

This paper customizes Bennett's equation for calculating lens power in chicken eyes from refraction, keratometry and biometry. Previously published data on refraction, corneal power, anterior chamber depth, lens thickness, lens radii of curvature, axial length and eye power in chickens aged 10-90 days were used to estimate Gullstrand's lens power and Bennett's lens power for chicken eyes, and to calculate the lens equivalent refractive index. Bennett's A and B constants for the front and back surface powers of the lens were calculated for data measured from day 10 to 90 at 10 day intervals, and mean customized constants were calculated. The mean customized constants for Bennett's equation for chicks were A=0.574±0.023 and B=0.379±0.021. As found previously, lens power decreases with age in chicks, while corneal power decreases and axial length increases. The lens equivalent refractive index decreases with age from 10 to 90 days after hatching. Bennett's equation can be used to calculate lens power in chicken eyes for studies on animal myopia, using standard biometry.

Activation of mammalian target of rapamycin signaling in skeletal muscle of neonatal chicks: Effects of dietary leucine and age

The mammalian target of rapamycin (mTOR) signaling pathway is necessary for cellular protein synthesis regulation. Leucine was reported to stimulate muscle protein synthesis in mammalian embryos and neonates, but in higher animals (chickens) the effect of dietary leucine on mTOR signaling is unknown. Thus, we investigated the effects of dietary leucine and age on mRNA expression and phosphorylation of mTOR as well as its downstream targets, ribosomal protein S6 kinase (S6K1) and eukaryotic initiation factor 4E binding protein 1 (4E-BP1) in chick pectoral muscles. One hundred eighty newly hatched male chicks were randomly assigned to 1 of 3 dietary leucine treatment groups (1.43, 1.73, and 2.03% leucine) for 14 d, respectively. Each treatment group consisted of 6 cages with 10 chicks each. On d 3, 7, and 14, plasma insulin and leucine were measured and target gene expression and phosphorylation was assessed. Dietary leucine influenced plasma leucine but not insulin, and plasma leucine and insulin declined with chick age. The mTOR, S6K1, and 4E-BP1 mRNA expression and phosphorylation within chick pectoral muscles were upregulated with increased dietary leucine but downregulated with increased chick age. Thus, high dietary leucine activates target of rapamycin signaling pathways in skeletal muscle of neonatal chicks to stimulate muscle protein synthesis, and this pathway is attenuated with aging.

Effect of age on contents of fatty acids in whole bodies of pheasants throughout their growth

The aim of the work was to evaluate the effect of age on the proportion of particular fatty acids in the whole bodies of pheasants fattened for up to 118 days of age. In the experiment, 232 chicks of common pheasants (Phasianus colchicus) were used. In the course of the experiment, the required number of pheasants was randomly selected for analysis at regular 10-day intervals. The age of pheasant chicks had a significant effect on the content of all fatty acids. Significant changes in the proportion of fatty acid groups were recorded mainly at 20, 40 and 60 days of age. By 20 days of age the proportion of monounsaturated fatty acids decreased considerably in relation to the increase in the content of polyunsaturated fatty acids, while the n6/n3 ratio decreased markedly. The content of monounsaturated fatty acids increased between day 20 and day 40, causing a simultaneous decrease in polyunsaturated fatty acids. From day 40, the monounsaturated fatty acid content increased gradually till the end of fattening, whereas the reverse trend was observed in the saturated fatty acid content in this period. As for polyunsaturated fatty acids, their presence increased from day 40 to day 60, followed by a gradual decrease till the end of fattening. The results of our work showed the different ability of pheasants to digest and utilize particular fatty acids with varying efficiency throughout their growth. The study brings new findings concerning changes in fatty acid composition of pheasants during fattening.

An experimental study measuring the effects of a tarsus-mounted tracking device on the behaviour of a small pursuit-diving seabird

Miniaturized tracking devices are taking a rapidly increasing role in studies measuring animal movement and other aspects of behaviour, especially for wide-ranging species such as seabirds that are difficult to observe otherwise. A crucial, but questionable criterion of such migration research is assuming that effects of tracking devices on animal behaviour are negligible, to ensure results of tracking studies are biologically relevant. To address this concern, we experimentally quantified effects of a 2 g (ca. 1.1% of body mass) geolocation device on crested auklet (Aethia cristatella) behaviour, including return rate, activity on the colony surface, and measures of reproductive performance in a two-year, two-part field study. In experiment 1, we fitted tracking devices (or identical dummy devices) to one mate of a breeding pair in nesting crevices, to quantify effects on reproductive performance and nest fidelity. In experiment 2, we assigned dummy devices to birds captured at the colony site surface, to quantify effects on social activity, return rate and provisioning behaviour. For birds tagged in crevices, we detected no effect on fledging success, or chick growth rate (mass and wing length). However, mass at fledging age of chicks provisioned with one tagged parent was significantly lower than control, and low nest site fidelity (compared to control birds) was observed for tagged birds. Individuals tagged on the colony surface showed significantly reduced colony surface activity, return rates and provisioning behaviour. This study shows strong ‘observer effects’ of an attached device well below the recommended size limit for wildlife tagging. Future studies should both quantify effects of attached devices and consider the biological relevance of measures of the behaviour of interest.

Whooping crane Grus americana chick mortality and management intervention

Translocation of captive‐reared animals is widely used as a tool for endangered species recovery. Frequently, translocated populations have relatively low initial productivity, requiring management intervention. A translocated population of whooping cranes Grus americana in central Wisconsin is such a case. We examined chick mortality for this population and used daily chick survival rates as our response variable to model several parameters including phenology, chick age, energetics and parent age and experience. We also developed and evaluated adoption techniques using sandhill cranes Grus canadensis to mitigate the effects of high chick mortality and increase the probability of fledging. Our results illustrate the challenges that translocated populations can face as they encounter novel breeding conditions. We found that whooping crane daily chick survival was relatively low and most mortality events occurred within the first 20 days. Our results indicated that variables related to age of the parents as well as the pair's previous chick rearing experience were useful for predicting daily chick survival. We found that sandhill crane foster parents readily accepted replacement chicks. We also demonstrated adopted chicks acceptance of foster parents and that the chicks' source (captive‐born vs wild‐born) did not affect success of the adoption. Chick adoption provides several management options that could be used to bypass the period when chicks experience the greatest mortality. Reducing chick mortality and developing techniques to increase the number of fledged chicks is paramount for whooping crane recovery as well as the recovery of other endangered bird species.

Sex and other sources of variation in the haematological parameters of White Stork Ciconia ciconia chicks

Biochemical and blood cell parameters have commonly been employed as useful minimally invasive indicators of the health or nutritional status of many spe- cies. Here, we present data on a suite of commonly mea- sured blood parameters from 342 White Stork Ciconia ciconia chicks of molecularly known sex. Samples were collected in western Poland during four breeding seasons (2005-2008). We examine whether sex, and also season (year), nesting locality, hatch date and brood size, con- tributed to variation in these blood parameters. There were significant seasonal differences in levels of the heterophil/ lymphocyte ratio, red blood cell count, haematocrit, hae- moglobin, mean corpuscular volume, mean corpuscular haemoglobin concentration, and particularly in white blood cell count. Significant nesting locality effects were detected in haemoglobin, mean corpuscular volume, mean corpus- cular haemoglobin and mean corpuscular haemoglobin concentration. Hatch date, virtually synonymous with chick age, significantly negatively influenced (i.e. later hatch dates (younger chicks when sampled) had lower values of red blood cell count, haematocrit, haemoglobin and mean corpuscular haemoglobin concentration. Male chicks had significantly lower levels of red blood cell count, haematocrit, haemoglobin and mean corpuscular haemoglobin concentration. There was a significant sex/ hatch date interaction for red blood cell count, haematocrit and haemoglobin. Brood size did not significantly affect any of the analysed parameters. Our work shows that blood parameters are influenced by many factors, including sex and age of individuals, and such factors may need to be taken into consideration when using blood parameters as indicators of health. Such considerations are especially critical in the establishment of reference ranges of blood parameters which may be of use in captive rearing of this endangered species.

Prefledging diet is correlated with individual growth in Greater Sage-Grouse (Centrocercus urophasianus)

ABSTRACT. The period of growth prior to fledging is a critical life stage for most birds, and shifts in diet during ontogeny may affect growth and development. We used nitrogen (δ15N) stable isotopes in feather tissue to quantify dietary composition and evaluate the relationship between diet and growth in prefledging Greater Sage-Grouse (Centrocercus urophasianus). Sequential sampling of δ15N from feather tissue that was synthesized throughout growth allowed us to evaluate changes in plant versus invertebrate contributions to chick diet during the first 28 days posthatch. Feathers became depleted in δ15N throughout growth, and Bayesian mixing models suggested that the proportional contribution of invertebrate nitrogen declined with chick age. We estimate that invertebrate contributions to the protein in chick diets decreased from 39% at 1 week to 23% at 4 weeks of age, which is consistent with previous research on sage-grouse that used traditional diet-sampling methods. Chicks with feather δ15N values tha...

Ontogeny of muscle bioenergetics in Adélie penguin chicks (Pygoscelis adeliae)

The ontogeny of pectoralis muscle bioenergetics was studied in growing Adélie penguin chicks during the first month after hatching and compared with adults using permeabilized fibers and isolated mitochondria. With pyruvate-malate-succinate or palmitoyl-carnitine as substrates, permeabilized fiber respiration markedly increased during chick growth (3-fold) and further rose in adults (1.4-fold). Several markers of muscle fiber oxidative activity (cytochrome oxidase, citrate synthase, hydroxyl-acyl-CoA dehydrogenase) increased 6- to 19-fold with age together with large rises in intermyofibrillar (IMF) and subsarcolemmal (SS) mitochondrial content (3- to 5-fold) and oxidative activities (1.5- to 2.4-fold). The proportion of IMF relative to SS mitochondria increased with chick age but markedly dropped in adults. Differences in oxidative activity between mitochondrial fractions were reduced in adults compared with hatched chicks. Extrapolation of mitochondrial to muscle respirations revealed similar figures with isolated mitochondria and permeabilized fibers with carbohydrate-derived but not with lipid-derived substrates, suggesting diffusion limitations of lipid substrates with permeabilized fibers. Two immunoreactive fusion proteins, mitofusin 2 (Mfn2) and optic atrophy 1 (OPA1), were detected by Western blots on mitochondrial extracts and their relative abundance increased with age. Muscle fiber respiration was positively related with Mfn2 and OPA1 relative abundance. Present data showed by two complementary techniques large ontogenic increases in muscle oxidative activity that may enable birds to face thermal emancipation and growth in childhood and marine life in adulthood. The concomitant rise in mitochondrial fusion protein abundance suggests a role of mitochondrial networks in the skeletal muscle processes of bioenergetics that enable penguins to overcome harsh environmental constraints.

Northern rockhopper penguins prioritise future reproduction over chick provisioning

As iteroparous species, seabirds must balance present against future reproduction. We used stable-isotope (SIA) and stomach content analysis (SCA) to examine the effects of sex, breeding stage, pre-moulting period, ontogeny and chick age on the diet of northern rockhopper penguins (NRP; Eudyptes moseleyi) breeding at the Tristan da Cunha archipelago during 2010. Stomach contents were obtained from birds during the guard and creche stages. δ 15 N and δ 13 C signatures of whole blood of adults were measured at Tristan Island (during the incubation, guard and creche stages), and of adult feathers at Tristan and nearby (-38 km) Nightingale Islands. δ 15 N and δ 13 C signatures of the whole blood of chicks were also measured during both stages. Adult pre-moult diets were significantly enriched in both elements at Nightingale compared to Tristan Islands. Adult female diet was dominated by zooplankton during the guard stage, and in both sexes by fish (predominantly Photichthyidae) in the creche stage. No effects of chick size within the guard stage, or of sex within the creche stage were observed on diet composition of adult birds. δ 13 C values of adult blood were higher in females relative to chicks, and in creche relative to guard stage individuals. δ 15 N values of blood showed a significant breeding stage x chick age interaction. Sex affected blood δ 15 N and δ 13 C only in the guard and incubation stages. Stage and sex interacted significantly on δ 13 C and δ 15 N signatures of adult feathers. NRP were opportunistic foragers, hunting in different areas during breeding and non-breeding periods, with different pre-moult foraging patterns observed in adults from colonies separated by only 38 km. Adults seemed to favour future reproduction, through brood reduction and by feeding chicks lower trophic level prey than they consumed themselves, although provisioning shifted from zooplankton to fish later in the breeding season.

Effects of Landscape-Scale Environmental Variation on Greater Sage-Grouse Chick Survival.

Effective long-term wildlife conservation planning for a species must be guided by information about population vital rates at multiple scales. Greater sage-grouse (Centrocercus urophasianus) populations declined substantially during the twentieth century, largely as a result of habitat loss and fragmentation. In addition to the importance of conserving large tracts of suitable habitat, successful conservation of this species will require detailed information about factors affecting vital rates at both the population and range-wide scales. Research has shown that sage-grouse population growth rates are particularly sensitive to hen and chick survival rates. While considerable information on hen survival exists, there is limited information about chick survival at the population level, and currently there are no published reports of factors affecting chick survival across large spatial and temporal scales. We analyzed greater sage-grouse chick survival rates from 2 geographically distinct populations across 9 years. The effects of 3 groups of related landscape-scale covariates (climate, drought, and phenology of vegetation greenness) were evaluated. Models with phenological change in greenness (NDVI) performed poorly, possibly due to highly variable production of forbs and grasses being masked by sagebrush canopy. The top drought model resulted in substantial improvement in model fit relative to the base model and indicated that chick survival was negatively associated with winter drought. Our overall top model included effects of chick age, hen age, minimum temperature in May, and precipitation in July. Our results provide important insights into the possible effects of climate variability on sage-grouse chick survival.

Parent Recognition in Chicks of the Ground-Nesting, Nidifugous Saunders's GullSaundersilarus saundersi

In birds, offspring-parent interactions play an essential role in facilitating offspring survival at nest-leaving. In contrast to nidicolous nestlings, nidifugous chicks are expected to hatch in ground nests, leave the nest soon after hatching, and presumably exhibit precise parent-offspring recognition during this time. Yet, some studies document variation in nidifugous behavior and offspring-parent recognition of semi-precocial chicks during the nest-leaving stage in the family Laridae. We examine patterns in nest-leaving age, mobile capacity, and parent recognition in wild and captive chicks of the Saunders's Gull Saundersilarus saundersi that is one of ground nesting and colonially breeding species. Our results indicated that the development of locomotor activity in nidifugous chicks coincided with the nest- leaving age. Soliciting behavior of experimental chicks increased with age, but they strongly discriminated vocalizations of pseudo-parents against unfamiliar adults only at the early stage of nest-leaving. We suggest that parent recognition by chicks during this short period may play a key role in facilitating their own survival while moving to a new environ- ment with their parents after leaving the nest. More studies using a comparative approach are needed to understand how nesting ecology, nest-leaving behavior, and parent-offspring interaction are interconnected in the members of the family Laridae.

Landscape factors and hydrology influence mercury concentrations in wading birds breeding in the Florida Everglades, USA

The hydrology of wetland ecosystems is a key driver of both mercury (Hg) methylation and waterbird foraging ecology, and hence may play a fundamental role in waterbird exposure and risk to Hg contamination. However, few studies have investigated hydrological factors that influence waterbird Hg exposure. We examined how several landscape-level hydrological variables influenced Hg concentrations in great egret and white ibis adults and chicks in the Florida Everglades. The great egret is a visual “exploiter” species that tolerates lower prey densities and is less sensitive to hydrological conditions than is the white ibis, which is a tactile “searcher” species that pursues higher prey densities in shallow water. Mercury concentrations in adult great egrets were most influenced by the spatial region that they occupied in the Everglades (higher in the southern region); whereas the number of days a site was dry during the previous dry season was the most important factor influencing Hg concentrations in adult ibis (Hg concentrations increased with the number of days dry). In contrast, Hg concentrations in egret chicks were most influenced by calendar date (increasing with date), whereas Hg concentrations in ibis chicks were most influenced by chick age, region, and water recession rate (Hg concentrations decreased with age, were higher in the southern regions, and increased with positive water recession rates). Our results indicate that both recent (preceding two weeks) hydrological conditions, and those of the prior year, influence Hg concentrations in wading birds. Further, these results suggest that Hg exposure in wading birds is driven by complex relationships between wading bird behavior and life stage, landscape hydrologic patterns, and biogeochemical processes.

Phytochemical and pharmacological evaluations of Polygonum lapathifolium stem extract for anthelmintic and antiemetic activity

The present study is an attempt to preliminary phytochemical investigation, anthelmintic and anti-emetic activity studies on methanolic extract of Polygonum lapathifolium stems. The phytochemical screening shows the presence of phytosterols, diterpens, amino acid & protein, alkaloid and flavonoids, those are responsible for antiviral, antibacterial, antiallergic, antihypertensive, antiarrythmic, hepatoprotective, anti-inflammatory effects in mammals. In Anthelmintic activity test (using Pheretima posthuma model) five concentrations (20, 40, 60, 80 and 100 mg/ml in distilled water) of extracts were used which involved the determination of time of paralysis (vermifuge) and time of death (vermicidal activity) of the worms, where the concentration of 60, 80 &100 mg/ml showed a significant anthelmintic activity. Observations were comparable with the standard drug at concentration of 10mg/ml of piperizine citrate. On the other hand, in anti-emetic test, emesis was induced by the oral administration of copper sulphate 50mg/kg body weight to four days age of young chicks using chick emesis model. The antiemetic activity was determined by calculating the mean decrease in number of retching in contrast with those of control disorders. The extracts (150 mg /kg orally) showed statistically significant antiemetic effect (90.45% Inhibition) compared with reference drug metoclopramide (50mg/kg intraperitoneally) which showed 82.48% Inhibition. From these observations, it was concluded that stems extracts have potential anthelmintic and anti-emetic properties. The plant may further be explored for its various pharmacological activities.DOI: http://dx.doi.org/10.3329/icpj.v2i3.13582 International Current Pharmaceutical Journal, February 2013, 2(3): 57-62

Monitoring the hatch time of individual chicken embryos

This study investigated variations in eggshell temperature (Tegg) during the hatching process of broiler eggs. Temperature sensors monitored embryo temperature by registering Tegg every minute. Measurements carried out on a sample of 40 focal eggs revealed temperature drops between 2 to 6°C during the last 3 d of incubation. Video cameras recorded the hatching process and served as the gold standard reference for manually labeling the hatch times of chicks. Comparison between Tegg drops and the hatch time of individuals revealed a time synchronization with 99% correlation coefficient and an absolute average time difference up to 25 min. Our findings suggest that attaching temperature sensors to eggshells is a precise tool for monitoring the hatch time of individual chicks. Individual hatch monitoring registers the biological age of chicks and facilitates an accurate and reliable means to count hatching results and manage the hatch window.

Age-Dependent Changes in the mRNA Levels of Neuropeptide Y, Proopiomelanocortin, and Corticotropin-Releasing Factor in the Hypothalamus in Growing Broiler Chicks

Lines of evidence suggest that hypothalamic neuropeptides have a physiological role in the regulation of food intake in mammals. However, little is known about the age-dependent change of hypothalamic neuropeptides in chicks. In this study, we investigated the age-dependent changes in hypothalamic mRNA levels of neuropeptide Y (NPY, an orexigenic neuropeptide), proopiomelanocortin (POMC, the precursor of anorexigenic neuropeptides), and corticotropin-releasing factor (CRF, a possible mediator in the POMC-induced anorexigenic pathway) in growing broiler chicks. The weights of body and abdominal adipose tissue of chicks were measured at 7, 14, 21, and 28 days of age, and the hypothalamic mRNA levels of NPY, POMC, and CRF were analyzed by real-time PCR. Hypothalamic NPY mRNA levels at 14 and 28 days of age were significantly (P<0.05) lower than that at 7 days of age. Hypothalamic POMC mRNA level at 28 days of age was significantly lower than that at 7 days of age. Hypothalamic CRF mRNA level was not affected throughout the experimental period. Abdominal adipose tissue weight was significantly increased after 14 days of age in chicks. Our findings demonstrated that the expressions of NPY and POMC are dependent on age in boiler chicken hypothalamus.

Low mercury contamination in Mediterranean gull Larus melanocephalus chicks in Greece

Mercury (Hg), a toxic heavy metal harmful to animals, commonly occurs in Mediterranean ecosystems. Mediterranean gull Larus melanocephalus numbers have declined considerably in Greece since the 1990s. Mediterranean gull chicks’ back feathers were therefore collected from three Greek colonies in different years between 1999 and 2009 to assess Hg pollution in this larid. Hg concentrations varied with arithmetic means ranging between 815 ng g−1 dry weight (dw) (Lafri Lagoon in 2000) and 1264 ng g−1 dw (Evros Delta in 2000), and values were independent of chick age, although significant among-year and among-site variations were found. Hg concentrations in Greek Mediterranean gull chick feathers were generally low and in fact lower than those associated with adverse effects in other bird species. Comparisons with other studies revealed that Hg concentrations in Mediterranean gulls from Greece were mostly lower than those found in other gull species elsewhere in the world. This study presents the first data on Hg contamination in the Mediterranean gull. The results might be useful in understanding and evaluating the birds’ exposure to this highly toxic pollutant and its impact on both local populations and the wider ecosystem.

Post-vaccinal reaction for some vaccines used against Newcastle disease in Sulaimaniyah province

This study was conducted to investigate the safety of the most commonly used Newcastle disease vaccines in Al-Sulaimaniyah province (LaSota and Clone30). A total of 225 one-day-old broiler chicks of Ross 308 breed were investigated for their maternal-derived antibody (MDA) titers by ELISA test. Subsequently, these chicks were divided randomly into 3 equal groups; ( 2 treatment groups, a T1 group which was vaccinated by LaSota vaccine and T2 group which was vaccinated by the Clone30 vaccine). and control non-vaccinated group. ELISA test was used to investigate the antibody titers against NDV in all groups on day 10 post second vaccination at 34 days of chicks age and tissue biopsies were obtained for histopathological examination from the trachea, spleen, Bursa of Fabricius and thymus to explore the tissue changes that may be induced by the vaccine. Significant variation was observed in the means of antibody titers against NDV between the control and treatment groups, whereas, no significant variation was observed between the treatment groups themselves. The histopathological examination results showed that a reactive lymphocytic response was observed in both treatment groups compared to the control group. In addition, focal epithelial sloughing and mucopurulent exudates were observed in the trachea of T1 group chicks only. The result of this study showed that the NDV vaccine of clone30 is approximate of the same efficiency and more secure than LaSota vaccine.

Translocation of Threatened New Zealand Falcons to Vineyards Increases Nest Attendance, Brooding and Feeding Rates

Anthropogenic landscapes can be rich in resources, and may in some cases provide potential habitat for species whose natural habitat has declined. We used remote videography to assess whether reintroducing individuals of the threatened New Zealand falcon Falco novaeseelandiae into a highly modified agricultural habitat affected the feeding rates of breeding falcons or related breeding behavior such as nest attendance and brooding rates. Over 2,800 recording hours of footage were used to compare the behavior of falcons living in six natural nests (in unmanaged, hilly terrain between 4 km and 20 km from the nearest vineyard), with that of four breeding falcon pairs that had been transported into vineyards and nested within 500 m of the nearest vineyard. Falcons in vineyard nests had higher feeding rates, higher nest attendance, and higher brooding rates. As chick age increased, parents in vineyard nests fed chicks a greater amount of total prey and larger prey items on average than did parents in hill nests. Parents with larger broods brought in larger prey items and a greater total sum of prey biomass. Nevertheless, chicks in nests containing siblings received less daily biomass per individual than single chicks. Some of these results can be attributed to the supplementary feeding of falcons in vineyards. However, even after removing supplementary food from our analysis, falcons in vineyards still fed larger prey items to chicks than did parents in hill nests, suggesting that the anthropogenic habitat may be a viable source of quality food. Although agricultural regions globally are rarely associated with raptor conservation, these results suggest that translocating New Zealand falcons into vineyards has potential for the conservation of this species.

Mercury Exposure May Suppress Baseline Corticosterone Levels in Juvenile Birds

Mercury exposure has been associated with a wide variety of negative reproductive responses in birds, however few studies have examined the potential for chick impairment via the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis regulates corticosterone levels during periods of stress. We examined the relationship between baseline fecal corticosterone metabolite concentrations and mercury concentrations in down feathers of recently hatched (<3 days) and blood of older (15-37 days) Forster's tern (Sterna forsteri) chicks in San Francisco Bay, California. Baseline fecal corticosterone metabolite concentrations were negatively correlated with mercury concentrations in blood of older chicks (decreasing by 81% across the range of observed mercury concentrations) while accounting for positive correlations between corticosterone concentrations and number of fledgling chicks within the colony and chick age. In recently hatched chicks, baseline fecal corticosterone metabolite concentrations were weakly negatively correlated with mercury concentrations in down feathers (decreasing by 45% across the range of observed mercury concentrations) while accounting for stronger positive correlations between corticosterone concentrations and colony nest abundance and date. These results indicate that chronic mercury exposure may suppress baseline corticosterone concentrations in tern chicks and suggests that a juvenile bird's ability to respond to stress may be reduced via the downregulation of the HPA axis.