Development of restoration techniques for Hawaiian thrushes: Collection of wild eggs,artificial incubation,hand‐rearing,captive‐breeding,and re‐introduction to the wild

From 1995 to 1999, two species of endemic Hawaiian thrushes, `Oma`o (Myadestes obscurus) and Puaiohi (M. palmeri), were captive‐reared and re‐introduced into their historic range in Hawai`i by The Peregrine Fund, in collaboration with the U.S. Geological Survey–Biological Resources Division (BRD) and the Hawai`i State Department of Land and Natural Resources. This paper describes the management techniques that were developed (collection of wild eggs, artificial incubation, hand‐rearing, captive propagation, and release) with the non‐endangered surrogate species, the `Oma`o; techniques that are now being used for recovery of the endangered Puaiohi. In 1995 and 1996, 29 viable `Oma`o eggs were collected from the wild. Of 27 chicks hatched, 25 were hand‐reared and released into Pu`u Wa`awa`a Wildlife Reserve. Using the techniques developed for the `Oma`o, a captive propagation and release program was initiated in 1996 to aid the recovery of the endangered Puaiohi. Fifteen viable Puaiohi eggs were collected from the wild (1996–1997) to establish a captive breeding flock to produce birds for re‐introduction. These Puaiohi reproduced for the first time in captivity in 1998 (total Puaiohi chicks reared in captivity 1996–1998 = 41). In 1999, 14 captive‐bred Puaiohi were re‐introduced into the Alaka`i Swamp, Kaua`i. These captive‐bred birds reproduced and fledged seven chicks in the wild after release. This is the first endangered passerine recovery program using this broad spectrum of management techniques (collection of wild eggs, artificial incubation, hand‐rearing, captive‐breeding, and release) in which re‐introduced birds survived and bred in the wild. Long‐term population monitoring will be published separately [BRD, in preparation]. Zoo Biol 19:263–277, 2000. © 2000 Wiley‐Liss, Inc.     

Capturing Common Loons during prenesting and nesting periods

ABSTRACT Several techniques have been used to capture Common Loons (Gavia immer), but effectiveness is limited during periods of the breeding season when loons do not have chicks. From 2005 to 2008, we studied loons in northern Wisconsin and used night lighting to capture loons on nests and also designed a lift net for capturing loons prior to nesting. At night, incubating loons were approached by boat and, when within about 30–60 m, we focused a spotlight on the loon and, once at the nest, captured loons using a landing net. Using this technique, we captured 23 loons in 29 attempts (79%). In addition, taped calls and loon decoys were used to entice prenesting, territorial loons into a shoreline‐based, lift‐net trap at a capture efficiency of 67% (10 captures in 15 attempts) during the second year of use. Our diurnal lift‐net trap and night‐light nest‐capture techniques allowed us to capture adult Common Loons during periods of the breeding season when previous investigators have found loons difficult to catch. These techniques may also be useful for capturing other species of territorial waterbirds, especially other species of loons.     

Mortality of common loons in New England, 1987 to 2000

Diagnostic findings are presented on 522 common loons (Gavia immer) found dead or moribund in New England (Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont, USA) between 1987 and 2000. Common loon numbers and range in New England have decreased from historic levels over the last century due to a number of proposed factors. Goals of this study were to identify and categorize causes of mortality and quantify natural versus anthropogenic causes. The majority of identifiable mortality in chicks was from intraspecific aggression (25%) and other causes of trauma (32%). Death in immature loons was primarily from fungal respiratory disease (20%) and trauma (18%). Causes of adult loon mortality differed significantly in breeding and wintering habitats. Wintering adults primarily died of trauma (17%) and infection (11%) and had significantly poorer body condition than breeding loons. In breeding adults, confirmed and suspected lead toxicosis from ingested fishing weights accounted for almost half of all mortality. Direct anthropogenic factors accounted for 52% of loon mortality in this study. Because of high carcass recovery rates, we believe these data are a good representation of loon mortality in New England. Results highlight the importance of human influences on conservation and management of the common loon in New England.     

Responses of breeding common loons to human activity in upper Michigan

Breeding populations of the common loon (Gavia immer) in Michigan have declined in the past several decades, resulting in classification of this species as threatened under state law. Factors responsible for the decline are unknown, but may include toxic contaminants, mortality in commercial fish nets, and human disturbance of breeding sites. To assess the latter possibility, 960 hours of observation were devoted to observing human-loon interactions on two sets of lakes, one with restricted human use (minimal or no shoreline development and open to canoe use only), and another with unrestricted use (varying amounts of shoreline development and motorboat traffic). Six mated pairs of loons on six restricted use (r-u) lakes were compared to eight loon pairs on seven open-use (o-u) lakes. The number of nests that hatched young per nest started was not significantly different between the two sets of lakes (7 of 13 (0.62) on r-u lakes vs 8 of 17 (0.47) on o-u lakes), despite significantly more human activity on o-u lakes. Chicks hatched per pair of loons were likewise not significantly different (1.1 vs 1.2 on r-u and o-u lakes, respectively). Fledging success was significantly lower on r-u lakes (7 chicks fledged of 11 hatched) than on o-u lakes (13 fledged of 13 hatched). Human activity on o-u lakes was 2–3 times that on r-u lakes during chick rearing, but time spent by adult loons tending and feeding chicks was not significantly different between the two types of lakes. The larger size of most o-u lakes may have allowed loons a greater opportunity to avoid human disturbance. Higher levels of human activity did not affect production of chicks by loons under the conditions observed, but these results should not be extrapolated to lakes experiencing much higher human use.     

Feeding behavior and modeled energetic intake of common loon (Gavia immer) adults and chicks on small lakes with and without fish

We examined the behavior of common loons, Gavia immer (Brünnich), breeding on small, shallow lakes in central Alberta, Canada that were naturally fishless or contained only small-bodied fishes (minnow lake). For both lake types, adults spent >90% of their time on the nesting lake and >50% of their time foraging. Adult loons on fishless lakes dove more frequently, but dives were of shorter duration than loons on lakes with fish. On two intensively studied fishless lakes, adults fed chicks macroinvertebrates, particularly leeches, whereas on a focal minnow lake, fish made up >70% of prey items delivered by adults. Chicks >36 days of age on a minnow lake spent >50% of their time foraging, whereas older chicks on fishless lakes were highly dependent on food provisioning by adults. Models based on observed foraging patterns indicated that prey size was a better predictor of success in meeting energetic requirements than was feeding behavior (e.g., dive rate, dive success). For most models, estimated energetic intake was higher for loons on minnow lakes than on fishless lakes. Our behavioral observations and model results are consistent with surveys in central Alberta that indicate that breeding Common Loons frequently establish territories on small lakes, but that chicks hatched on lakes completely lacking fish rarely fledge and only if sufficient large invertebrates such as leeches are available.     

Captive breeding for reintroduction: influence of management practices and biological factors on survival of captive kaki (black stilt)

An important component of the restoration strategy for the critically endangered kaki or black stilt (Himantopus novaezelandiae) is captive breeding for release. Since 1981 1,879 eggs were collected from wild and captive pairs, with birds laying up to four clutches. Eggs were incubated artificially and most chicks reared by hand until released as juveniles (about 60 days) or sub‐adults (9–10 months). Because survival in captivity is a significant determinant of the number of birds available for release, we wished to identify sources of variation in mortality to assess potential impacts of management on productivity. Hatchability was 78% for captive‐laid eggs and 91% for wild‐laid eggs. Survival of hatched eggs was 82% by 10 months of age for both wild and captive birds. Most egg mortality occurred early in incubation and around hatching: the timing of mortality was unaffected by whether birds were captive or wild, hybrid or pure kaki, or when eggs were laid. Heavier hatchlings showed higher initial survival, as did chicks from wild parents. Hatchlings from fourth‐laid eggs showed lowest survival, even though hatchling mass tended to increase with hatch order. Survival of chicks subjected to major health interventions was 69% after 4 months. No differences in survival were found between different genders, hybrids and pure kaki, hand‐reared or parent‐reared birds, chicks hatching early or late in the season, different seasons, different‐sized groups of chicks, chicks reared in different brooders, juveniles kept in different aviaries, and chicks from subsequent clutches. Birds subjected to minor health interventions were equally likely to survive as healthy chicks (82%). Survival was high despite aggressive management (quadruple clutching and collecting late in the season). Differences between captive and wild birds suggest further improvements could be made to captive diet. Wide variation in hatchability between parent pairs substantiates the practice of breaking up poorly performing pairs. Zoo Biol 0:1–16, 2005. © 2005 Wiley‐Liss, Inc.     

Breeding condors in captivity for release into the wild

Recognizing the decline of the South American Condor in some parts of its range and the highly endangered status of the California condor, the New York Zoological Society developed a captive-breeding program for South American condors. This program was designed to produce techniques applicable to hand-rearing of either species of condor. Once condors were successfully reared in captivity, it became imperative to develop techniques to ensure that captive-reared condor chicks could be released into the wild, could survive there, and could interact naturally with other wild condors. Captive-bred hand-reared condor chicks were taken to Northwestern Peru and successfully released into the wild.     

Captive breeding and rearing of critically endangered Mauritius fodies Foudia rubra for reintroduction

In‐situ captive rearing of endangered passerines for reintroduction has rarely been used as a conservation tool. Nests of Mauritius fodies threatened with predation by introduced mammalian predators were harvested from the wild, and chicks were reared to independence for release onto an offshore, predator‐free island. The daily probability of the survival was higher in captivity than in the wild, and 69 chicks were reared to fledging of which 47 would have been expected to fledge in the wild. Harvesting of nests probably had little impact on the wild population. Captive breeding trials on Mauritius fodies showed that large numbers of individuals could be produced for a release program from a small number of pairs if enough space was provided. Artificial incubation of passerine eggs and rearing of chicks can be used to increase the productivity of endangered taxa. Zoos can play an important role in in‐situ conservation programs through provision of avicultural expertise and training of local staff. Zoo Biol 27:255–268, 2008. © 2008 Wiley‐Liss, Inc.     

Territory occupancy by common loons in response to disturbance,habitat, and intraspecific relationships

Structure and distribution of animal territories are driven by a variety of environmental and demographic factors. A peninsular population of common loons (Gavia immer) nests on lakes in northwestern Montana, but does not occupy all apparently suitable breeding territories, suggesting unexplained limitations on population growth. To evaluate territorial dynamics of breeding loons in Montana, we created and tested occupancy models that evaluated the hypothesized effects of disturbance, habitat, and intraspecific relationships on territory occupancy by common loons in Montana from 2003 to 2007. Model-averaged results indicated that the abundance of feeding lakes within 10 km (i.e., forage quality) and the number of territorial pairs within 10 km (i.e., density of loons) were equally supported and related to probabilities of occupancy. We found substantial support that the population was in a state of equilibrium, with the numbers of occupied territories stable in time, but not space. We also found that density of territorial pairs was related to the likelihood that an existing territory would be abandoned, but did not influence the establishment of new territories, suggesting the presence of territorial pairs could be a stronger indicator of territory quality to loons than physical lake characteristics. Our index of human disturbance was not well-supported compared to other factors. Our results suggest management for stable or growing loon populations could be achieved using long-term monitoring and protection of occupied territorial lakes and nearby feeding lakes, because these factors most influenced the probability of occupancy of surrounding lakes. © 2011 The Wildlife Society.     

Factors influencing productivity of common loons (Gavia immer) breeding on circumneutral lakes in Nova Scotia, Canada

Common loons (Gavia immer) are top predators that are sensitive to biotic and abiotic conditions associated with their breeding lakes, so factors such as lake chemistry and human activity or disturbance are thought to influence their seasonal and long-term reproductive success. We used two indices of loon productivity to evaluate (1) temporal patterns and (2) relationships with physical and chemical lake characteristics and human activities. Data collected from 1991 to 2000 by volunteers of the Canadian Lakes Loon Survey (CLLS) in Nova Scotia showed that loon productivity, as indexed by both the proportion of resident pairs that produced at least one large young (P_s1) and the proportion of successful pairs that produced two large young (P_s2), did not vary substantially from year to year and showed no linear trend from 1991 to 2000. Average estimates (1991–2000) for P_s1 and P_s2 were 0.49 ± 0.02 and 0.43 ± 0.03, respectively, and the mean number of chicks per residential pair over that time was 0.75 ± 0.04. We found that human disturbance and shoreline development did not influence loon productivity during the prefledging stage on lakes surveyed by CLLS volunteers. Proportion of resident pairs rearing at least one large young was independent of dissolved organic carbon (DOC) concentrations of breeding lakes, but there was a positive relationship between the proportion of successful pairs rearing two large young and DOC. Both indices of loon productivity tended to be negatively correlated with lake pH. These results were not consistent with other findings that loon productivity generally declines with lake acidity, but likely reflect the preponderance of circumneutral (pH 6.5–7.0) lakes surveyed by the CLLS volunteers in Nova Scotia.     

Alarm responses are maintained during captive rearing in chicks of endangered kaki

The maintenance of species-specific behavioural repertoires and traditions is an important but often implicit goal of conservation efforts. When captive rearing is used as a conservation practice, it becomes critical to address its possible implications for the social and behavioural traits of developing individuals. In particular, animals must retain or acquire many of their behavioural abilities to increase the likelihood of survival upon release into the wild. This study investigated the behavioural development of critically endangered kaki (black stilt: Himantopus novaezelandiae ) chicks reared without live adult conspecifics. The captive rearing programme included playbacks of adult kaki alarm calls during cleaning and handling of precocial chicks housed as groups. We used videotaped observations and playback experiments to address the following questions: do kaki chicks respond differentially to (1) familiar versus unfamiliar adult kaki alarm calls and (2) conspecific alarm versus heterospecific control vocalizations. Adult-naïve kaki chicks exhibited a varied behavioural repertoire over their early development. In multivariate analyses, when age was statistically controlled, chicks showed responses to familiar and unfamiliar alarm calls that were similar in magnitude. In contrast, following conspecific alarm calls chicks had longer average latencies to resume pre-playback activities than following heterospecific vocalizations. Although the generality of these conclusions is limited by experimental constraints stemming from working with an endangered species, the findings suggest that current management techniques produce captive-reared kaki for release into the wild that possess many of the behavioural and auditory recognition skills that are required for survival.     

Captive breeding and reintroduction of the endangered masked bobwhite

Efforts to restore the endangered masked bobwhite (Colinus virginianus ridgwayi) to its former range have required 1) habitat acquisition, restoration, and preservation; 2) captive propagation; and 3) reintroduction of captive-bred stock. In its role to recover the masked bobwhite, the Patuxent Wildlife Research Center (U.S. Fish and Wildlife Service) has refined captive breeding techniques; provided captive-produced stock for release; conducted field research on the distribution, limiting factors, and habitat characteristics of this species; and developed release methods. Techniques for the husbandry and captive management, breeding, artificial incubation and hatching of eggs, and rearing of young of the masked bobwhite have been developed. Successful reintroduction techniques for the masked bobwhite have included prerelease conditioning and/or cross-fostering of captive-reared masked bobwhite chicks to a wild-caught, related, vasectomized bobwhite species and their release to the wild as family units. In addition, the establishment by the U.S. Fish and Wildlife Service of the Buenos Aires National Wildlife Refuge in 1985 has further enhanced the potential for establishing a self-sustaining population of the masked bobwhite in the U.S. Through continued releases and active management of habitat, therefore, it is believed that the masked bobwhite can become permanently established at the refuge to ensure its continued survival in the wild.     

Effects of spatial disturbance on common loon nest site selection and territory success

The common loon (Gavia immer) breeds during the summer on northern lakes and water bodies that are also often desirable areas for aquatic recreation and human habitation. In northern New England, we assessed how the spatial nature of disturbance affects common loon nest site selection and territory success. We found through classification and regression analysis that distance to and density of disturbance factors can be used to classify observed nest site locations versus random points, suggesting that these factors affect loon nest site selection (model 1: Correct classification = 75%, null = 50%, K = 0.507, P < 0.001; model 2: Correct classification = 78%, null = 50%, K = 0.551, P < 0.001). However, in an exploratory analysis, we were unable to show a relation between spatial disturbance variables and breeding success (P = 0.595, R² = 0.436), possibly because breeding success was so low during the breeding seasons of 2007–2008. We suggest that by selecting nest site locations that avoid disturbance factors, loons thereby limit the effect that disturbance will have on their breeding success. Still, disturbance may force loons to use sub-optimal nesting habitat, limiting the available number of territories, and overall productivity. We advise that management efforts focus on limiting disturbance factors to allow breeding pairs access to the best nesting territories, relieving disturbance pressures that may force sub-optimal nest placement. © 2011 The Wildlife Society     

DOES PREY BIOMASS OR MERCURY EXPOSURE AFFECT LOON CHICK SURVIVAL IN WISCONSIN?

Abstract: Past studies suggest that the productivity of common loons (Gavia immer) is lower on acidic lakes in northern Wisconsin, USA, than on neutral lakes. Two hypotheses have been proposed to explain low chick survival: (1) reduced food consumption related to changes in prey communities on lower pH lakes and (2) high mercury (Hg) exposure on lower pH lakes. To address these hypotheses, we quantified prey and Hg consumption by loon chicks on 51 lakes and survival on 55 lakes ranging in pH from 4.9 to 9.5 in northern Wisconsin in 1995 and 1996. The time adults spent providing prey to chicks was unrelated to lake pH but increased with number of chicks and chick age. The number of prey caught per provisioning time declined as lake pH declined because adults made fewer dives, not because success of prey capture declined. Chicks consumed more insect larvae on acidic lakes and more crayfish (Family Astacidae) on neutral lakes. Biomass consumed ranged from an average 1.99 ± 1.05 (SE) g/hr/chick during the first week of a chick's life to a peak of 7.93 ± 1.93 g/hr/chick during the eighth week. Biomass intake per chick body weight (g/W_g/hr) declined with lake acidity but was not related to chick survival (P = 0.25). Although the Hg concentration in the 3 major prey species was positively related to lake acidity and blood Hg level of chicks at a lake, total Hg consumption (μg/W_g/hr) was highest on moderately acidic lakes rather than on the most acidic lakes. We suggest that loon chick survival in northern Wisconsin lakes is more likely related to prey availability than to Hg exposure. When we removed from our analysis 1 lake where 2 11-day-old chicks were killed by predators, chick survival was negatively related to lake acidity but not to biomass or Hg consumption. We discuss mechanisms of Hg excretion that may allow young chicks to survive on acidic lakes in northern Wisconsin despite high Hg intake.     

Provisioning by captive yellow-tufted honeyeaters (Lichenostomus melanops gippslandicus) acting as foster parents for helmeted honeyeater chicks (L. m. cassidix)

A captive breeding program is being conducted with the endangered helmeted honeyeater (Lichenostomus melanops cassidix). Establishment of breeding stock involved cross fostering helmeted honeyeater chicks to breeding yellow-tufted honeyeaters (Lichenostomus melanops gippslandicus). Data were collected on provisioning rates and food preferences of the foster parents in feeding chicks of the helmeted subspecies. Feeding rates varied from 5–6 each hour per chick in the first week to 8–10 per chick in week 3 and were similar for both one- and two-chick broods. Chicks were considered independent by 6 weeks. Provisioning by the foster parents was evenly divided between the sexes. Insects were the main food item fed to nestlings (89.9%). Moths and mealworms were the two most frequently selected items and were the two largest items available. The continued increase of the captive population may provide individuals for release to the wild population, and techniques developed through captive management will help conserve wild populations. © 1994 Wiley-Liss, Inc.     

Comparative nest survival of three sympatric loon species breeding in the Arctic

Identifying factors influencing nest survival among sympatric species is important for understanding and managing sources of variation in population dynamics of individual species. Three species of loons nest sympatrically in northern Alaska and differ in body size, life history characteristics, and population trends. We tested the effects of competition, nest site selection, and water level variations on nest survival of Pacific Gavia pacifica, yellow‐billed G. adamsii, and red‐throated loons G. stellata on the Arctic Coastal Plain in Alaska. Although overall nest survival rates did not differ between species, the factors influencing nest survival varied. Nest site selection influenced nest survival for Pacific and yellow‐billed loons, with both species having high nest survival when nesting on islands and peninsulas, likely due to a reduction in access by terrestrial predators. However, on mainland shorelines, Pacific loons had lower nest survival than yellow‐billed loons, and used a higher proportion of vegetation mats for nest sites suggesting that their smaller body size makes them less adept at nest defense. Nest site selection did not influence nest survival of red‐throated loons corresponding to our result of no nest site preferences by this species. Initiation date had a strong influence on nest survival for Pacific and yellow‐billed loons with nests laid earlier having higher survival. Pacific and yellow‐billed loon nests were susceptible to flooding due to precipitation, which contrasted with red‐throated loons that nest on smaller lakes with lower water level variations. Competition did not affect nest survival for any of the species likely due to most territorial encounters occurring prior to incubation. The only influence we found on red‐throated loon nest survival was differences among years. Our results indicate that loons chose nest sites based on predation risk and that factors influencing breeding success of closely related species may differ under similar breeding conditions.     

Juvenile survival in common loons Gavia immer: effects of natal lake size and pH

Survival is a vexing parameter to measure in many young birds because of dispersal and delayed impacts of natal rearing conditions on fitness. Drawing upon marking and resighting records from an 18‐yr study of territorial behavior, we used Cormack–Jolly–Seber analysis with Program MARK to estimate juvenile survival and its predictors in a population of common loons Gavia immer. In addition, we investigated predictors of chick mass, survival and inter‐sibling size disparity in two‐chick broods. Both small size and low pH of natal lakes predicted poor survival among chicks and juveniles; thus, features of the natal environment have both immediate and lasting effects on fitness. The pH × stage interaction retained in our MARK models indicates that the detrimental impact of lake chemistry on fitness diminishes with time; the retention of pH × lake size as a predictor of chick mass and condition pinpoints small lakes as those where acidity impacts chicks most severely. Our adjusted estimate of 0.53 probability of for survival to age 3 suggests that loon populations are healthier than often supposed.     

Activity budgets of a marked common loon (Gavia immer) nesting population

A newly devised nightlighting technique was used to capture breeding adult common loons (Gavia immer) at the Seney National Wildlife Refuge in northern Michigan in 1989. The behaviors of 6 pairs of known-sex, color-marked common loons were subsequently quantified during the breeding cycle in 1990. Collected observational data indicate that foraging, resting, locomotion, and preening were frequent throughout the breeding cycle. Time spent foraging was greatest during the pre-nesting period (53 to 57%), but declined significantly during the nesting and post-nesting periods (p<0.05). Time spent foraging during the pre-nesting period was similar to that of fall and winter studies. During the pre-nesting period adult loons spent about 15% of the time in locomotion; this was significantly greater than the other time periods (p<0.05) and is attributed to selecting a nest site. During the nesting cycle, almost half of each bird's time spent was nest-sitting. Sexual differences were negligible during nest-sitting. Resting and chick-rearing were the predominant behaviors during the post-nesting period and were responsible for the biggest difference in parental duties. Time spent preening declined from 8% during the pre-nesting period to 4 to 5% during the post-nesting period. Time spent by nesting pairs to produce chicks is approximately 10% during pre-nesting, 48 to 49% during nesting, and between 38 to 44% during post-nesting. By quantifying and establishing behavioral standards, subtle abnormalities or changes can be detected to better manage for viable common loon populations.     

Aufzucht von Chilemeerespelikane (Pelecanus occidentalis thagus) im Vogelpark Walsrode mit Vergleichen zu anderen publizierten Erfahrungen mit Pelikanen

The probable world first captive breeding success in Chilean Brown Pelican (Pelecanus occidentalis thagus) in captivity is reported. Two chicks were hand reared at Walsrode Birdpark, Germany in 2006. Parents were imported in October 2005 and were wild birds that had been injured and subsequently rescued. All 10 adult birds demonstrated detrimental and chronically handicaps. First eggs were laid in January 2006. Eggs were incubated artificially at 37.1 °C and 56% rel. humididty. Two chicks hatched after 33 days of incubation. First feeding was made one day after hatching in the morning. Food was given 5 times a day. Until the 8th day after hatching, exclusively cut naked baby rats were fed. For stimulating the digestion and providing a good intestinal flora Lactobacillus powder was used and food was warmed up before application. After 8 days the diet was changed to fish. For development see figures. Worth to mention is the black-purple colour of the freshly hatched chicks which became successively paler with age. Also the development of the feather areas is characteristic for this (sub)-species. Taxonomy is discussed with some morphological arguments that are typical for subspecies. Nevertheless, some indications of possible breeding barriers between subspecies could support the suggestions for species status. Hatching and rearing data are compared with dates from other zoos and species of pelicans. The good development of the Walsrode birds based on the data and methods described leaves this article useful as a reference guideline for hand rearing pelicans.