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.     

Hissing females of great tits (Parus major) have lower breeding success than non‐hissing individuals

Antipredator strategies vary remarkably between individuals within populations. Parents tend to take greater risks when brood value is increased. Moreover, individuals consistently differ in a whole suite of correlated behaviours that may cause distinctive responses to predators. It is likely that individual differences in antipredator behaviour may co‐vary with proxies for fitness such as reproductive success. We used a 4‐year data from wild great tits (Parus major) to test whether passive and active antipredator strategies (females with no response vs. those giving hissing calls towards a nest predator) during the incubation stage can reflect variation in breeding success. Although clutch size did not depend on hissing behaviour, the number of surviving offspring from eggs and neonates to fledglings was higher for non‐hissing than hissing birds. We conclude that females with distinct antipredator strategies can prioritize different fitness components.     

Effects of capture and video‐recording on the behavior and breeding success of Great Tits in urban and forest habitats

Behavioral research often involves capturing and video‐recording birds, but these procedures may have undesired effects on the behavior of birds that have rarely been quantified. In addition, birds in urban and more natural areas may differ in their sensitivity to disturbance. We examined the possible effects of both capturing, weighing and measuring, and taking a blood sample, and the presence of video‐cameras on the behavior of male and female Great Tits (Parus major) breeding in urban and forest habitats. Using a 2 × 2 block design, we compared the behavior and breeding success of parents that either were or were not captured on their nests a few days before behavioral observations, and of parents that either were or were not habituated to the presence of a concealed video‐recorder mounted on nest boxes. We found no significant effects of habituation to the camera on bird behavior, but males captured in their nest boxes were more vigilant and hesitated longer before entering nest boxes, and also had slightly lower provisioning rates than males that had not been captured. Captured females also tended to be more vigilant than females that had not been captured, but their provisioning rates were not affected. Capturing males also influenced the behavior of their non‐captured mates, but capturing females had no effect on the behavior of their non‐captured mates. We found no difference in the effects of capture on Great Tits in urban and forest habitats, and our treatments also had no effect on the mass, size, and survival of nestlings until fledging. Our results suggest that, for Great Tits, being captured results in sex‐dependent behavioral effects that can last for at least several days. As such, we suggest that the possibility of similar effects in other species of birds should be considered in behavioral studies where birds must be captured, and recommend either that behavioral data be collected before capturing birds or that all birds in a study should be captured and handled in a standardized way.     

Contemporary breeding biology of critically endangered Regent Honeyeaters: implications for conservation

Identifying factors influencing the demographics of threatened species is essential for conservation, but a lack of comprehensive demographic data often impedes the effective conservation of rare and mobile species. We monitored breeding of critically endangered and semi‐nomadic Regent Honeyeaters Anthochaera phrygia (global population c. 100 pairs) over 3 years throughout their range. Overall nest success probability (0.317) was highly spatially variable and considerably lower than previous estimates for this (and many other honeyeater) species, as was productivity of successful nests (mean 1.58 juveniles fledged). Nest surveillance revealed high predation rates by a range of birds and arboreal mammals as the primary cause of nest failure. An estimated 12% of pairs either failed to establish a territory or their nests did not reach the egg stage. We also found a male bias to the adult sex ratio, with an estimated 1.18 males per female. Juvenile survival for the first 2 weeks after fledging was high (86%). Management interventions that aim to increase nest success in areas of low nest survival must be investigated to address an apparent decline in reproductive output and avoid extinction of the Regent Honeyeater. We show that temporal and spatial variation in the breeding success of rare and highly mobile species can be quantified with robust population monitoring using sampling regimens that account for their life histories. Understanding the causes of spatio‐temporal variation in breeding success can enhance conservation outcomes for such species through spatially and temporally targeted recovery actions.     

Nesting behavior and breeding success of Hoatzins

ABSTRACT.   Hoatzins ( Opisthocomus hoazin ) are the only member of the family Opisthocomidae and are found only in forests in the Amazon and Orinoco river basin of South America. Although locally common in riparian habitats, information about their natural history is based almost exclusively on observations from gallery forests in the "llanos" (savannahs) of Venezuela. We investigated the nesting activities of Hoatzins in a primary rainforest in Amazonian Ecuador from 1995 to 2000. At our study site, Hoatzins live and breed in the inundated forests that surround lakes and river channels. Egg laying occurred from February to July and from September to November, but always peaked in April, May, and June. The mean clutch size was 2.4 ± 1.1 eggs ( N = 291; range = 1–7), but 51% of all clutches contained two eggs. The mean duration of the incubation period was 32 ± 1.5 d ( N = 20) and, overall, 17% of Hoatzin nests fledged at least one young. The main cause of nest failure was predation, with birds and snakes being the most frequent predators. Hoatzin reproduction was closely linked to the rainy season, and such timing may be influenced by increased food availability (high water levels cause leaf fall and the subsequent growth of new leaves coincides with the beginning of the feeding period of the young) and reduced risk of nest predation by mammalian predators when water levels are high. Our results indicate that the breeding biology of Hoatzins in tropical rainforest habitat, including small clutch sizes and low annual reproductive success, is similar to that of tropical passerines and provides further support for the existence of typical life history characteristics for tropical birds.     

Cliff characteristics,neighbour requirements and breeding success of the colonial Cape Vulture Gyps coprotheres

The breeding success of endangered colonial nesting species is important for their conservation. Many species of Gyps vultures form large breeding colonies that are the foci of conservation efforts. The Cape Vulture is a globally threatened species that is endemic to southern Africa and has seen a major reduction in its population size (≥ 50% over 48 years). There is evidence that breeding colonies are prone to desertion as a result of human disturbance. Factors that influence the occupancy and breeding success of individual nest‐sites is not fully understood for any African vulture species. We investigated cliff characteristics and neighbour requirements of the Msikaba Cape Vulture colony, a major breeding colony in the southern node of the population in the Eastern Cape, South Africa, together with their nest‐site occupation and breeding success over 13 years. In total, 1767 breeding attempts were recorded. Nest‐sites that had a higher elevation, smaller ledge depth, greater total productivity and were surrounded by conspecifics were more likely to be occupied, although the amount of overhang above the nest was not an important predictor of occupancy. In accordance with occupation, nest‐sites with a smaller ledge depth had higher breeding success; however, nests with a greater overhang were also more successful and height of the nest‐site was not an important predictor of breeding success. The breeding success of a nest‐site in a given year was positively influenced by the number of direct nest neighbours, and nests in the middle of high‐density areas had greater breeding success. This suggests that maintaining a high nest density may be an important consideration if declines of reproducing adults continue. Breeding success declined over the study period, highlighting the effects of a temporal variation or observer bias. Our results identified optimal nest‐site locations (ledge depths of 1 m, at a height of 180 m) and their effects on breeding success. This information can be used for planning reintroduction efforts of the endangered Cape Vulture and for their ongoing conservation.     

The evolution of obligate interspecific brood parasitism in birds

We present a simple analytical model to investigate the conditionsfor the evolution of obligate interspecific brood parasitismin birds, based on clutch size optimization, when birds canlay more eggs than their optimal clutch size. The results showthat once intraspecific parasitism has appeared (i.e., femalesstart to spread their eggs over their own and other nests) the evolutionarily stable number of eggs laid in its own nest decreases.Two possible ESSs exist: (1) either the evolutionarily stablenumber of eggs laid in its own nest is larger than zero, anda fraction of the total number of eggs is laid parasitically(i.e., intraspecific parasitism); and (2) either the evolutionarilystable number of eggs laid in its own nest is zero and all eggs are laid parasitically. Since all females lay parasitically,this could favor the evolution of obligate interspecific broodparasitism. The key parameter allowing the shift from intraspecificto obligate interspecific parasitism is the intensity of density-dependentmortality within broods (i.e., nestling competition). Strongnestling competition, as in altricial species, can lead toan ESS where all eggs are laid parasitically. Altricial speciesare, therefore, predicted to evolve more easily toward obligate interspecific parasitism than precocial species. These predictionsfit the observed distribution of brood parasitism in birds,where only one species out of 95 obligate interspecific parasitesexhibits a precocial mode of development. Different nestlingsurvival functions provided similar findings (i.e., obligatebrood parasitism is more likely to evolve in altricial species),suggesting that these results are robust with respect to themain assumption of the model.     

The breeding biology of Bennett's wallaby (Macropus rufogriseus jruticus) in South Canterbury,New Zealand

Abstract

The lipid and amino acid composition of the egg contents of captive dwarf cassowary (Casuarius bennetti) was investigated. Although the proportions of triacylglycerol (65%) and phospholipids (27%) were similar to those found in domestic hen eggs, the fatty acid content of the lipids was different. Egg lipids contained less than 2% linoleic acid and this is probably inadequate for chick development. An oil of high linoleic acid content — such as com oil — as a supplement to the maternal diet could improve the breeding success of these birds in captivity.     

Mismatches between breeding success and habitat preferences in Hen Harriers Circus cyaneus breeding in forested landscapes

During the past century, the upland breeding areas of Hen Harriers in Ireland have been extensively afforested. There is no evidence that this species avoids breeding in heavily forested landscapes and, indeed, young commercial forests in their second rotation are often selected as nest‐sites. However, Hen Harriers have coexisted with these forested areas for only a few decades and it is possible that such landscapes are suboptimal. We examined the relationship between breeding success and habitat using a dataset spanning three years and four study areas in the south and west of Ireland. We assessed whether nest success and fledged brood size were related to habitat type, both at the nest‐site and in the surrounding landscape. Neither measure of breeding productivity was related to total forest cover or to percentage cover of closed canopy forest in the landscape. However, in a subset of areas, high cover of second‐rotation pre‐thicket (young forests planted on land from which a first rotation has already been harvested) in the surrounding landscape was associated with low levels of breeding success. This may be due to factors related to predation, disturbance or prey availability. The fact that second‐rotation pre‐thicket is a preferred habitat for nesting in Ireland suggests that Hen Harriers may be making suboptimal decisions in the landscapes available to them.     

Characteristics of reproductive biology and proximate factors regulating seasonal breeding in captive golden-headed lion tamarins (Leontopithecus chrysomelas)

Reproduction is highly demanding in terms of energy expenditure, and the costs and benefits associated with postponing or investing in a reproductive effort are crucial determinants of an individual's fitness. Understanding the reproductive potential of a species under varying ecological conditions offers important insights into the dynamics of its social system. This study provides the first detailed analysis of the reproductive potential of wild- and captive-born golden-headed lion tamarins (Leontopithecus chrysomelas) under captive conditions, based on studbook data compiled during 1984-2000. Litters produced by wild-born females breeding in captivity are similar in size to litters observed in the wild, but smaller than litters of captive-born females. The more stringent ecological conditions experienced by wild-born females during maturation may result in a lifelong effect on litter size. However, interbirth intervals are shorter for wild-born than captive-born females. The relatively smaller burden of infant care that results from having smaller litters may allow wild-born females to sustain the next pregnancy sooner. Reproduction in the Brazilian captive population is highly seasonal for both wild-born females and females born in captivity in Brazil. Changes in photoperiod over a year provide a proximate explanation for changes in the proportion of conceptions and births per month. Outside Brazil, breeding occurs year-round, and no clear birth peak is apparent. Information from field reports that could be used to relate this finding to ecological factors, such as resource availability, is unavailable.     

沙漠石蜂的筑巢材料和蜂巢结构

沙漠石蜂Megachile(Chalicodoma) desertorum Morawitz为多种植物的传粉昆虫,在西鄂尔多斯地区是多种濒危植物和荒漠建群植物的重要传粉者。在该地区研究沙漠石蜂的筑巢场所、筑巢材料和蜂巢结构。共调查统计5148个蜂巢的筑巢场所和朝向;选择4个土壤表层成分不同的筑巢地,分别测定其筑巢沙土的机械组成、pH值和土壤紧实度;定点连续观察整个筑巢过程。结果表明:沙漠石蜂95.80%的巢建于岩石表面;土墙、灌木枝条、水泥柱及钢窗框上的巢室数均较少。83.1%的巢室建在东向一面;南向14.2%,西向2.4%,北向仅0.3%;筑巢材料为沙土和唾液制成的泥浆,所用沙土的pH值在8.18～9.34之间、紧实度在1.28～1.84g/cm3之间,其中粒径为0.06～0.15mm的沙土比例最高;1个蜂巢一般由4～10个巢室组成。说明该蜂喜欢将巢室建在朝向东方的岩石表面;筑巢材料主要由唾液和以碱性的粒径为0.06～0.15mm左右的沙土构成。也说明是对干旱炎热的荒漠环境的适应。     

Breeding biology of Orange‐breasted (Harpactes oreskios) and Red‐headed (H. erythrocephalus) trogons in Khao Yai National Park,Thailand

ABSTRACT As tropical habitats continue to be cleared or degraded, obtaining basic information about the ecology of birds in intact habitats is essential for understanding their life histories. We studied the breeding biology of Orange‐breasted Trogons (Harpactes oreskios) and Red‐headed Trogons (H. erythrocephalus) in Khao Yai National Park in Thailand from 2003 to 2009. Nests were in excavated cavities in well‐rotted stumps or other tree parts. Mean cavity heights were 2.1 m (N= 19) for Orange‐breasted Trogons and 2.0 m (N= 49) for Red‐headed Trogons. Eggs were laid every other day. For Orange‐breasted Trogons, the mean clutch size was 2.4 ± 0.1 (SE) eggs (N= 17); incubation periods for two nests were 17 and 18 d, respectively, and the nestling period ranged from 12 to at least 14 d (N= 4). For Red‐headed Trogons, the mean clutch size was 2.6 ± 0.1 eggs (N= 48), the mean incubation period was 18 d (N= 9), and the mean nestling period was 13.4 d (N= 5). In both species, both males and females excavated nest sites, incubated eggs, and brooded and provisioned nestlings. Only females incubated and brooded at night, and males provisioned nestlings more than females. Breeding seasons lasted from January to March for Orange‐breasted Trogons, and from late February to July for Red‐headed Trogons. Mayfield estimates of nest success were 8% and 9% for Orange‐breasted and Red‐headed trogons, respectively. Unusual for cavity nesters, nest failure due to predation was high and nestling periods short. The low nesting success is typical of many other tropical species, but considerably lower than reported for some Neotropical trogons, possibly due to the unenclosed structure of the nests of these Asian trogons.     

Notes on the breeding biology of Rufous Potoos (Nyctibius bracteatus) in lowland Ecuadorian Amazon

Five species of potoos occur in Ecuador, with Rufous Potoos (Nyctibius bracteatus) being one of the least known. We monitored a nest site of Rufous Potoos in a lowland forest in the Ecuadorian Amazon and provide information about the behavior of a nestling and one or more adults. Observations were conducted opportunistically from 10 August to 10 September 2018, and an infrared heat‐and‐motion activated camera was used to monitor the nest site from 11 September to 13 November 2018. We recorded 2006 10‐s videos of the nestling and/or adult(s) that we used to quantify behavior. The nestling spent most of its time perching (53%) and stretching (20.7%). Beginning when ~ 23 d old, the nestling began exercising its flight muscles and did so with increasing frequency over time. Adult behaviors included perching while brooding the nestling (55%), stretching (24%), flying (10.4%), and feeding the nestling (10.4%). The duration of the nestling period, ~ 2 mo, in our study was similar to that reported previously for this species. Our observations suggest that the breeding and nestling behavior of Rufous Potoos is similar to that of other Nyctibius species. However, additional studies are needed to better document the behavior of Rufous Potoos during the incubation period.     

Effects of nestboxes on the breeding biology of Southern House Wrens Troglodytes aedon bonariae in the southern temperate zone

Nestboxes are known to increase clutch size, enhance breeding success and affect the social mating system of several cavity nesters. Although in recent years various cavity nesters have been studied in nestboxes in South America, the effects of boxes on the biology of the study species are unknown. We evaluated the effects of nestboxes on the breeding biology and social mating system of Southern House Wrens Troglodytes aedon bonariae by comparing birds breeding in nestboxes and tree cavities in two cattle ranches in Buenos Aires Province, Argentina. Southern House Wrens nesting in boxes had higher breeding success but, contrary to studies on the temperate zone, we did not find differences in clutch size between Wrens breeding in nestboxes and tree cavities. The main causes of nest failure in tree cavities were nest predation and flooding of the cavity (70 and 23% of the failures, respectively) while in nestboxes predation and desertion were the most important causes of failure (38 and 34% of the failures, respectively). The social mating system of Southern House Wrens is monogamy with biparental care, and neither was affected by the boxes. Males did not attract secondary females to additional nestboxes; however, nestboxes are safer breeding sites than tree cavities, and females seemed to prefer males with nestboxes on their territory. These results suggest that nest quality alone might be not enough for secondary females to accept polygyny.     

Conspecific nest parasitism is associated with inequality in nest predation risk in the common goldeneye (Bucephala clangula)

Previous studies of the role of nest predation in conspecificnest parasitism have not taken into account the possibilitythat predation risk may not be randomly distributed among nestsites and that breeding individuals may use different cues toassess the risk and adjust their reproductive tactic betweenyears accordingly. Especially in cavity-nesting species, therole of nest predation in conspecific nest parasitism has beendownplayed, while the role of nest site limitation has beenhighlighted. Using both observational and experimental data,I show that in the common goldeneye (Bucephala clangula), acavity-nesting species in which conspecific nest parasitism iscommon, predation risk varies considerably between nest sitesand does not follow a random expectation. The inequality inpredation risk between nest sites also showed up in the occurrenceof parasitized nests in an experimental setup. Nests parasitizedin year t were more frequent in those nest sites that were notdepredated during the previous nesting attempt in year t - nthan in nest sites that were depredated and in control nestsites that had not been used for nesting before. A nest siteaddition experiment revealed that conspecific nest parasitismwas not associated with nest site limitation. My findings givesupport for the hypothesis that nest predation is an importantecological factor explaining conspecific nest parasitism ingoldeneyes.