Foraging Skills Research Articles

Monkeys who experience more feeding competition utilize social information to learn foraging skills faster

Animals must learn foraging skills to successfully survive and reproduce but the sources of interindividual variation in learning are poorly understood. For example, there is little consensus on the role motivation plays, even though it is a key factor impacting learning outcomes in humans. Here, we conduct a field experiment on a wild primate to investigate whether an individual’s vulnerability to feeding competition impacts their motivation to learn a beneficial foraging technique. We provided a group of monkeys with a food reward (i.e., a half banana) that needed to be retrieved from a box. The monkeys discovered an efficient technique that consistently allowed them to retrieve the banana quickly, decreasing the risk of food loss to competitors. We found that individuals who frequently experienced feeding competition learned this efficient technique significantly faster than individuals who rarely foraged in the presence of a dominant competitor. They appeared to use social learning to learn faster as they were more attentive to the handling techniques others used and improved their foraging skills after opportunities to observe a skilled demonstrator. These findings support that an individual’s vulnerability to feeding competition impacts their motivation to learn foraging skills that reduce food loss to competitors.

The early life of king penguins: ontogeny of dive capacity and foraging behaviour in an expert diver.

The period of emancipation in seabirds, when juveniles change from a terrestrial existence to a life at sea, is associated with many challenges. Apart from finding favourable foraging sites, they have to develop effective prey search patterns and physiological capacities that enable them to capture sufficient prey to meet their energetic needs. Animals that dive to forage, such as king penguins (Aptenodytes patagonicus), need to acquire an adequate breath-hold capacity, allowing them to locate and capture prey at depth. To investigate the ontogeny of their dive capacity and foraging performance, we implanted juvenile king penguins before their first departure to sea and also adult breeders with a data-logger recording pressure and temperature. We found that juvenile king penguins possess a remarkable dive capacity when leaving their natal colony, enabling them to conduct dives in excess of 100 m within their first week at sea. Despite this, juvenile dive/foraging performance, investigated in relation to dive depth, remained below the adult level throughout their first year at sea, probably reflecting physiological limitations as a result of incomplete maturation. A significantly shallower foraging depth of juveniles, particularly during their first 5months at sea, could also indicate differences in foraging strategy and targeted prey. The initially greater wiggle rate suggests that juveniles fed opportunistically and also targeted different prey from adults and/or that many of the wiggles of juveniles reflect unsuccessful prey-capture attempts, indicating a lower foraging proficiency. After 5months, this difference disappeared, suggesting sufficient physical maturation and improvement of juvenile foraging skills.

Seasonal activity levels of a farm-island population of striated caracaras (Phalcoboenus australis) in the Falkland Islands

BackgroundAnimals need adaptive strategies to cope with seasonal changes in prey availability to survive and reproduce, which can include migrating, prey-switching, or reducing metabolic needs. Human settlements can disrupt spatiotemporal patterning in resource availability, which can affect animals’ foraging success, particularly for juveniles who are behaviorally developing and learning efficient foraging skills. Here, we investigate behavioral responses of juvenile striated caracaras, a near-threatened scavenging falconid, to seasonally migratory seabird prey and a farm settlement on Saunders Island, Falklands. We deployed accelerometer–GPS dataloggers (n = 27) to measure seasonal differences in daily and hourly vectorial dynamic body acceleration (VeDBA; an activity index measured in gravitational g) and space use, and investigated seasonal variation in body mass of the tagged subset and an additional 65 caracaras.ResultsJuvenile caracaras were overall similarly active in winter and summer. However, during winter, caracaras made the most of limited daylight by increasing average daytime activity (winter males: 0.16 ± 0.03 g, summer males: 0.09 ± 0.01 g, winter females: 0.12 ± 0.02 g, summer females: 0.08 ± 0.01 g). During winter, both sexes increased the percentage of daylight spent in high activity (winter males: 35 ± 5%, summer males: 21 ± 3%, winter females: 25 ± 6%, summer females: 16 ± 3%, p < 0.001) and ranged nearly 4 times farther (95% kernel density estimate winter: 2.36 ± 0.96 km2, summer: 0.61 ± 0.20 km2; p < 0.001). Furthermore, on a daily scale, males were 21% more active than females year-round (24-h average VeDBA: males 0.07 ± 0.01 g, females 0.06 ± 0.01 g; p < 0.01). We did not observe a significant seasonal difference in mass.ConclusionThat caracaras’ daily activity and body mass did not vary between seasons suggests that wintering birds on Saunders are meeting resource requirements despite the absence of seasonally migratory prey. We hypothesize that human subsidies may mitigate the effect of seasonal food limitations. Further research should include studies on seasonal energetics to improve our understanding of baseline body condition, and comparative studies on other islands and including adults to understand the importance of human subsidies.

Visits at artificial RFID flowers demonstrate that juvenile flower-visiting bats perform foraging flights apart from their mothers

During the transition from parental care to independent life, the development of adequate foraging skills is a major challenge for many juvenile mammals. However, participating in their parents’ knowledge by applying social learning strategies might facilitate this task. For several mammals, communal foraging of adults and offspring is suggested to be an important mechanism in mediating foraging-related information. For the large mammalian taxon of bats, only little is known about foraging-related social learning processes during ontogeny. It is often suggested that following their mothers during foraging flights would represent a valuable option for juveniles to socially learn about foraging, e.g., where to find resource-rich foraging patches, but explicit tests are scarce. In the present study, we investigated the foraging behavior of juvenile flower-visiting bats (Glossophaga soricina) in a dry forest in Costa Rica. We tested whether recently volant, but still nursed pups perform foraging flights alone, or whether pups follow their mothers, which would enable pups to socially learn where to feed. For that, we trained mothers and pups to feed from artificial flowers with a RFID reading system and, subsequently, conducted a field experiment to test whether RFID-tagged mothers and pups visit these flowers communally or independently. Unexpectedly, pups often encountered and visited artificial flowers near the day roost, while mothers rarely did, suggesting that they foraged somewhere further away. Our results demonstrate that still nursed juveniles perform foraging flights apart from their mothers and might learn about the spatial distribution of food without participating in their mother’s knowledge, for instance, by following other conspecifics or applying individual learning strategies. An initial potential lack of foraging success in this period is likely compensated by the ongoing maternal provisioning with breast milk and regurgitated nectar during daytime. Our results contribute to the growing body of research on the ontogeny of mammalian foraging behavior in general.

Introducing foraging skills

Foraging is an essential life skill and will help children develop their understanding of the natural world and local environment. Chloe Webster explains how foraging can be implemented into outdoor play.

Ontogeny of foraging behaviour in juvenile red-footed boobies (Sula sula)

The early life stages represent a crucial period that can strongly influence population dynamics. We studied the development of foraging behaviour in the red-footed booby, a tropical seabird with an extensive post-fledging care period (3 to 6 months). Adults and juveniles were observed from shore and tracked at sea using GPS loggers over 3 consecutive 12-day periods. Juveniles initially made a majority of flights inland, likely to practice flying, and formed groups of up to 10 juveniles before making short trips at sea. They left the island later and returned earlier than the adults, allowing them to be fed on the nest. Over time, juveniles left the colony alone more frequently and increased the range of their trips while remaining significantly closer to the colony than the adults. They spent more time intensively foraging (slow and sinuous trajectory) than adults, which could reflect attempts to capture prey. Juveniles foraged independently of their parents but associated frequently with congeners, particularly during area-restricted search (ARS) behaviour. The extensive post-fledging care period observed may be explained by the need to develop proper foraging skills adapted to tropical waters, where resources are particularly scarce and unpredictable.

No evidence for self-recognition in a small passerine, the great tit (Parus major) judged from the mark/mirror test

Self-recognition is a trait presumed to be associated with high levels of cognition and something previously considered to be exclusive to humans and possibly apes. The most common test of self-recognition is the mark/mirror test of whether an animal can understand that it sees its own reflection in a mirror. The usual design is that an animal is marked with a colour spot somewhere on the body where the spot can only be seen by the animal by using a mirror. Very few species have passed this test, and among birds, only magpies have been affirmatively demonstrated to pass it. In this study, we tested great tits (Parus major), small passerines, that are known for their innovative foraging skills and good problem-solving abilities, in the mirror self-recognition test. We found no indication that they have any ability of this kind and believe that they are unlikely to be capable of this type of self-recognition.

Social Attention in the Two Species of Pan: Bonobos Make More Eye Contact than Chimpanzees.

Humans’ two closest primate living relatives, bonobos and chimpanzees, differ behaviorally, cognitively, and emotionally in several ways despite their general similarities. While bonobos show more affiliative behaviors towards conspecifics, chimpanzees display more overt and severe aggression against conspecifics. From a cognitive standpoint, bonobos perform better in social coordination, gaze-following and food-related cooperation, while chimpanzees excel in tasks requiring extractive foraging skills. We hypothesized that attention and motivation play an important role in shaping the species differences in behavior, cognition, and emotion. Thus, we predicted that bonobos would pay more attention to the other individuals’ face and eyes, as those are related to social affiliation and social coordination, while chimpanzees would pay more attention to the action target objects, as they are related to foraging. Using eye-tracking we examined the bonobos’ and chimpanzees’ spontaneous scanning of pictures that included eyes, mouth, face, genitals, and action target objects of conspecifics. Although bonobos and chimpanzees viewed those elements overall similarly, bonobos viewed the face and eyes longer than chimpanzees, whereas chimpanzees viewed the other elements, the mouth, action target objects and genitals, longer than bonobos. In a discriminant analysis, the individual variation in viewing patterns robustly predicted the species of individuals, thus clearly demonstrating species-specific viewing patterns. We suggest that such attentional and motivational differences between bonobos and chimpanzees could have partly contributed to shaping the species-specific behaviors, cognition, and emotion of these species, even in a relatively short period of evolutionary time.

Slow development of foraging skills and parental costs of family-living in a semi-precocial, non-cooperatively breeding bird

Family-living has been recognized as a first step in the evolution of cooperative breeding. Although delayed juvenile dispersal occurs in non-cooperative breeders, studies investigating family formation in these species are rare. Juveniles delay natal dispersal in response to ecological constraints of dispersal and/or benefits of philopatry, with parents predicted to adjust their tolerance towards independent offspring according to their direct fitness benefits. Consequently, precocial chick development is often associated with low parental care and short family association. White-breasted mesites (Mesitornis variegata) are group-living but non-cooperatively breeding birds that live in saturated habitats, whose semi-precocial young exhibit large variation in the timing of natal dispersal. We investigated whether the development of foraging skills of nutritionally independent juvenile mesites affects their dispersal decisions. Additionally, because parents show aggression towards older offspring particularly around the subsequent breeding season, we studied whether family-living is costly for parents. Our results indicate that juveniles develop their foraging skills slowly, that juveniles with poorer foraging skills tend to disperse later, and that adults experience foraging and reproductive costs from extended juvenile association. Therefore, it may be beneficial for less skilled juveniles to remain longer in the safety of the family when breeding vacancies are scarce. Furthermore, parental costs of family-living may trigger parental aggression towards juveniles, resulting in the dissolution of families and the lack of cooperative breeding in this species. This study highlights the importance of cost-benefit analyses from both the parents’ and offspring’s perspective to understand family stability and, hence, evolutionary routes towards cooperative breeding.

Post-fledging dispersal of king penguins (Aptenodytes patagonicus) from two breeding sites in the South Atlantic.

Most studies concerning the foraging ecology of marine vertebrates are limited to breeding adults, although other life history stages might comprise half the total population. For penguins, little is known about juvenile dispersal, a period when individuals may be susceptible to increased mortality given their naïve foraging behaviour. Therefore, we used satellite telemetry to study king penguin fledglings (n = 18) from two sites in the Southwest Atlantic in December 2007. The two sites differed with respect to climate and proximity to the Antarctic Polar Front (APF), a key oceanographic feature generally thought to be important for king penguin foraging success. Accordingly, birds from both sites foraged predominantly in the vicinity of the APF. Eight king penguins were tracked for periods greater than 120 days; seven of these (three from the Falkland Islands and four from South Georgia) migrated into the Pacific. Only one bird from the Falkland Islands moved into the Indian Ocean, visiting the northern limit of the winter pack-ice. Three others from the Falkland Islands migrated to the eastern coast of Tierra del Fuego before travelling south. Derived tracking parameters describing their migratory behaviour showed no significant differences between sites. Nevertheless, generalized linear habitat modelling revealed that juveniles from the Falkland Islands spent more time in comparatively shallow waters with low sea surface temperature, sea surface height and chlorophyll variability. Birds from South Georgia spent more time in deeper waters with low sea surface temperature and sea surface height, but high concentrations of chlorophyll. Our results indicate that inexperienced king penguins, irrespective of the location of their natal site in relation to the position of the APF, develop their foraging skills progressively over time, including specific adaptations to the environment around their prospective breeding site.

Mass and bathymetry influences on the foraging behaviour of dependent yearling New Zealand sea lions (Phocarctos hookeri)

Juvenile foraging ability is limited due to physiological and morphological constraints. Restricted foraging skills can result in reduced juvenile survival, which can lead to population decline. Given the important role mass plays in influencing foraging behaviour and survival, we deployed satellite-linked time-depth recorders (TDRs) on seven dependent yearling New Zealand sea lions (Phocarctos hookeri) over three seasons from 2008–2010 at the New Zealand subantarctic Auckland Islands to study how mass influenced at sea movements and diving behaviour. Mass was significantly negatively related to dive depth and descent rate, indicating yearling diving behaviour may be influenced by their mass. The yearlings demonstrated inter-individual variation in foraging locations and strategies. This individual variation was likely attributed to the bathymetry of different foraging areas dictating possible dive depths. Thus, when studying foraging behaviour, in addition to physiological and morphological influences, researchers must examine external factors such as the physical characteristics of the foraging habitat.

How to explain the unusually late age at skill competence among humans

Humans stand out among primates and other mammals in reaching adult-level foraging skills very late in development, well after the onset of reproduction. The aim of this paper is to place this unusual human skill development into a broader comparative context. Among birds and mammals in general, duration of immaturity, indexed by age at first reproduction (AFR), and adult brain size have undergone correlated evolution. This pattern is consistent with two causal processes: AFR is either limited by the time needed to learn adult-level skills (needing to learn) or by the energy needed to grow brain and body to full size (energetic constraints). We tested predictions arising from these two hypotheses with data retrieved from the published literature for 57 mammal and bird species. First, most mammals reach adult-level foraging skills well before the developmental period is completed, implying that energy constraints determine the age at first reproduction, whereas most birds reach adult-level foraging skills around the time of maturity, suggesting time needed for skill acquisition determines the onset of reproduction. Second, within mammals we found that with increasing niche complexity, the age of adult-level skill competence moves closer to the age at first reproduction. Third, when looking at how adult-level skills can be reached later, we found that gregariousness, slow conservative development and post-weaning provisioning allow mammals to reach their skills later. Finally, in species with intense sharing of resources (such as cooperative hunters) competence in foraging skills may even reach peak values after age of first reproduction. We conclude that the human pattern of skill acquisition could arise because our hominin ancestors added cooperative breeding and hunting to the slow development they had as great apes with increasingly complex niches. This result provides a broad biological foundation for the embodied capital model.

Age-related prey selectivity and foraging efficiency of Olrog's Gulls (Larus atlanticus) feeding on crabs in their non-breeding grounds

Foraging ecology is an essential component of the life history of a species and a good understanding of foraging ecology is especially important for threatened species where prey populations may be adversely affected by anthropogenic processes. This study examines age-related prey selection and prey-handling efficiency of Olrog's Gulls (Larus atlanticus) during the non-breeding season at the Mar Chiquita Coastal Lagoon, Argentina. Foraging behaviour and diet were determined by focal observation and compared with the availability of prey within their foraging patches. All captured prey were crabs, with the Burrowing Crab (Neohelice granulata) more commonly taken than the Mud Crab (Cyrtograpsus angulatus). Gulls consumed small and medium-sized crabs in higher proportions than those available and consumed more male crabs. Juvenile Gulls had longer handling times than older birds. Handling times increased with size of crabs independently of the sex of prey. The handling efficiency of adults was significantly higher than that of subadults, which in turn was higher than that of juveniles. These differences between age-classes could be attributed to differential foraging skills and social subordination of juvenile Gulls. The reasons for avoidance of large crabs is not certain but might be because carapaces are not easily digested, there is a higher risk of injury, or capture of large crabs may result in more intense kleptoparasitic interactions, among others.

Parent age differentially influences offspring size over the course of development in Laysan albatross

AbstractOffspring growth and survival are predicted to be higher for older parents, due to a variety of mechanisms, such as increased breeding experience or greater investment favored by low residual reproductive value. Yet the extent to which parent age affects offspring viability is likely to vary between different aspects of growth and survival, perhaps being most pronounced at the most stressful stages of reproduction. We studied the link between parent age and nestling growth and survival in the Laysan albatross, a long‐lived seabird with a mean first breeding age of 8 years. Offspring of older parents were more likely to survive to fledging. Among those that did fledge, nestlings of older parents grew more rapidly. However, parent age did not influence the eventual asymptotic size that nestlings reached before fledging: fast‐growing nestlings of older parents reached 90% of asymptotic size roughly 1 week sooner, but slow‐growing nestlings of younger parents eventually caught up in size before fledging. Older parents bred c. 2 days earlier than younger parents, but hatch date did not explain observed variation in offspring success. The extent to which parent age accounted for variation in size of individual nestlings was not constant but peaked near the midpoint of development. This could reflect a time period when demands on parents reveal age‐based differences in parental quality. Overall, growth and survival of offspring increased with parent age in this species, even though the late age of first breeding potentially provides a 7‐year period for birds to hone their foraging skills or for selection to eliminate low‐quality individuals.

Rolling Prey and the Acquisition of Aerial Foraging Skills in Northern Mockingbirds

I describe an unusual food-handling behavior performed by juvenile Northern Mockingbirds (Mimus polyglottos). In the course of one morning, I observed juvenile Northern Mockingbirds repeatedly roll several prey items down the incline of a roof in Charlottesville, Virginia. I discuss this behavior in the context of the development of aerial foraging skills.

Postfledging parental care in Savannah sparrows: sex, size and survival

We investigated postfledging parental care in a philopatric population of Savannah sparrows,Passerculus sandwichensis , breeding on Kent Island, New Brunswick, Canada in an effort to understand the factors influencing adult birds' decisions about parental investment in offspring. Brood division was not based on offspring sex: male and female parents were equally likely to care for sons or daughters. The total duration of parental care, from hatching to independence, was similar for sons and daughters (median=23 days), regardless of the sex of the care-giving parent. The duration of parental care also corresponded closely to the time required for juveniles to acquire basic foraging skills. Despite high levels of extrapair paternity, male Savannah sparrows invested as much in postfledging care and were as effective as females in caring for fledglings, based on recruitment of fledglings into the breeding population the following year. Male parents were more likely to care for smaller fledglings and for offspring from early broods (presumably to enable females to dedicate their efforts towards second clutches). Caring for fledglings was costly for parents: survivorship decreased as a function of the duration of postfledging parental care and the number of fledglings cared for. Parental survivorship, however, was not affected by the sex of the fledglings cared for. This study suggests that sex-biased provisioning may be unlikely except in species with strongly sexually dimorphic offspring, biased offspring sex ratios and sex-biased natal dispersal. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.

Temporal records of δ13C and δ15N in North Pacific pinnipeds: inferences regarding environmental change and diet

Sea lion and seal populations in Alaskan waters underwent various degrees of decline during the latter half of the twentieth century and the cause(s) for the declines remain uncertain. The stable carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) isotope ratios in bone collagen from wild Steller sea lions (Eumetopias jubatus), northern fur seals (Callorhinus ursinus) and harbor seals (Phoca vitulina) from the Bering Sea and Gulf of Alaska were measured for the period 1951-1997 to test the hypothesis that a change in trophic level may have occurred during this interval and contributed to the population declines. A significant change in δ(15)N in pinniped tissues over time would imply a marked change in trophic level. No significant change in bone collagen δ(15)N was found for any of the three species during the past 47years in either the Bering Sea or the Gulf of Alaska. However, the (15)N in the Steller sea lion collagen was significantly higher than both northern fur seals and harbor seals. A significant decline in δ(13)C (almost 2 ‰ over the 47years) was evident in Steller sea lions, while a declining trend, though not significant, was evident in harbor seals and northern fur seals. Changes in foraging location, in combination with a trophic shift, may offer one possible explanation. Nevertheless, a decrease in δ(13)C over time with no accompanying change in δ(15)N suggests an environmental change affecting the base of the foodweb rather than a trophic level change due to prey switching. A decline in the seasonal primary production in the region, possibly resulting from decreased phytoplankton growth rates, would exhibit itself as a decline in δ(13)C. Declining production could be an indication of a reduced carrying capacity in the North Pacific Ocean. Sufficient quantities of optimal prey species may have fallen below threshold sustaining densities for these pinnipeds, particularly for yearlings and subadults who have not yet developed adequate foraging skills.

Social tactics of pigs in a competitive foraging task: the ‘informed forager’ paradigm

Studies of the social dynamics in foraging groups have focused primarily on birds, rodents and nonhuman primates. We extended the study of animal social tactics to the domestic pig, Sus scrofa, by using an experimental analogue of natural foraging skills, the ‘informed forager’ paradigm. We investigated the behaviour of 16 pigs foraging in pairs in an arena in which food had been hidden in one of eight monopolizable buckets. Before each pair trial, one of the pigs, the ‘informed’ pig, was given privileged knowledge about the location of the food during a solitary search trial. The ‘noninformed’ pig was naı̈ve about the location of the food during pair trials, but heavier than its informed partner and thus able to displace the latter from the baited bucket. By first focusing on the informed pigs' behaviour, we show that pigs are able to remember and relocate the food site. They found the food in relocation trials, using fewer bucket investigations than expected of a random searcher. Second, by focusing on the noninformed pigs, we show that pigs are able to exploit the knowledge of others by following them to a food source. They investigated more buckets immediately after their informed partners significantly more often than expected by chance and required fewer bucket investigations to find the food in pair trials than expected from a random searcher, but not in solitary search trials. We discuss these latter findings with reference to social foraging tactics.

DNA fingerprinting reveals female preference for male parental care in Savannah Sparrows.

According to sexual selection theory, females choose mates to ensure access to high quality resources, male parental care, or good genes. This last hypothesis has been hotly debated on both theoretical and empirical grounds. In contrast, female preference for male parental care has received less attention, primarily because the potential benefits of paternal effort seem obvious. The fitness relations are less clear in double-brood species, however, because females can base mating decisions on their prior experience with male parental care. Here, the extent of male parental care delivered to first-brood offspring may indicate male genetic quality and/or be the target of female manipulation via her subsequent mating fidelity. In Savannah Sparrows (Passerculus sandwichensis), multi-locus DNA fingerprinting of 203 adults and young revealed substantial female infidelity in first and second broods: overall, 24 of 80 first-brood young (30%) and 13 of 80 second-brood young (16.3%) were the product of extra-pair fertilizations. Among 12 females altering fidelity between broods, absolute male feeding rate to first-brood offspring was a strong, positive predictor of change in female fidelity. Because the extent of male parental care reflects a male's viability, the data support a 'good-genes' interpretation.

A risk assessment for lead in birds

Ecotoxicologists and ecologists have examined the effects of pollutants on individuals and populations largely in terms of one or only a few effects. Yet the recent trend toward a holistic approach to ecological risk assessment suggests that a rigorous paradigm should be applied to toxicants, from hazard identification to risk characterization. Recent discussions have recognized that an up-front problem formulation phase is more critical in ecological risk assessment than it is for human health risk assessment. In this article a modified environmental health risk assessment paradigm is used to examine the risk of lead to birds. This risk analysis is largely conceptual, based on laboratory and field data, and incorporates information currently available. The model expands the hazard identification phase to create a target identification phase that includes the identification of receptors, endpoints, relationships, spatial and temporal scales, and indicators. The target identification phase is unique to the particular hazard, species, population, or community being examined. Lead can cause mortality, or can indirectly affect populations through effects on the food base, avian behavior, reproductive success, and recruitment. Lead can (1) decrease the abundance and availability of prey, (2) bioaccumulate in prey causing increased lead toxicosis in predators, or (3) increase prey availability by interfering with its hiding or escape behavior. Moreover, lower abundance of prey can lead to starvation or nutrient deficiencies, which amplify the absorption and retention of lead. Lead also causes decreases in clutch and egg size, mortality of embryos and nestlings, depression of growth, and deficits in behavior that affect survival. Lead decreases migratory behavior, and increases vulnerability to cold stress, hunters, and other predators. Research needs for evaluating the risk of lead in birds include obtaining data on (1) metal dynamics within various tissues as a function of dose and time since initial exposure, (2) low-level effects on embryos, (3) effects on chicks following fledging and in the period prior to recruitment, (4) effects on adult foraging skills and reproductive behavior, and (5) the relationship between effects from exposure in the laboratory and those from exposure in the wild. This latter point is extremely important, particularly if wild birds have other means of ridding the body of lead not available or less apparent to laboratory birds.