Influencing Breeding Success Research Articles

Replacement Broods in a Cavity Nesting Bird Species under High Predation Pressure in Primeval Forest

Predation is one of the most important factors influencing breeding success. Many bird species suffer from high losses because of predators. I studied breeding success and replacement broods in the Red-breasted Flycatcher Ficedula parva. The Red-breasted Flycatcher is a small bird breeding in natural holes in dense deciduous and mixed forests of Europe. Data were collected during twelve breeding seasons in a primeval forest, in the Bialowieża National Park, Northeast Poland, the best preserved and protected area of the Białowieża Forest with a rich community of birds and mammals including predators. Almost half of the broods of the Red-breasted Flycatcher were lost and most of them because of predation. In cases where the brood was lost in the period of egg laying or incubation, females tended to lay a replacement clutch. First and replacement nest-sites differed insignificantly in characteristics, but new clutches were always laid in a new site. Out of 68 broods, in which a loss was found, replacement broods were recorded in 47.1% cases. Replacement clutches were much smaller and pairs raised significantly fewer fledglings. The proportions of successful and lost broods were similar in the first and replacement attempts (56.1%, and 46.7%, respectively). Red-breasted Flycatchers choose shallow nest-sites that allow the females to observe their surroundings. This allows the female to escape from the nest when a predator approaches, increasing the possibility of a repeat clutch and the attainment of breeding success in the same season.

Breeding Success of Cape Vultures (Gyps coprotheres) at Colonies in the Tswapong Hills, Botswana

The endangered Cape Vulture (Gyps coprotheres), a southern African endemic, breeds on precipitous cliffs in various habitats. Some colonies of this cliff-nesting species are found in the southeast (Mannyelanong Hill) and east (Tswapong Hills and adjacent complexes) of Botswana. Of six breeding sites studied in the Tswapong Hills complex from 1992 to 1999, only two large colonies near the villages of Goo-Moremi (Bonwalenong site) and Goo-Tau (Manong Yeng site) and one small colony near Lerala (Kukubye site) still hold breeding vultures. In 2017 and 2018 we used direct observations to estimate the breeding population and breeding success of Cape Vultures at the Bonwalenong and Manong Yeng colonies, and we compared our findings with data from the 1990s. We identified 261 nests in 2017 and 362 nests in 2018, and monitored them throughout the breeding season. Breeding success at the two sites differed significantly between the 2 yr of our study (2017 and 2018). However, breeding success at Manong Yeng in 2017–2018 did not differ significantly from that documented in the earlier study (1992–1999). Our results also suggested relatively stable numbers of breeding pairs in the Tswapong Hills between 1992–1999 and 2017–2018. Cape Vultures in the Tswapong Hills require continued monitoring and research to better understand population dynamics and the key factors influencing breeding success and nestling survival.

Breeding success of the Himalayan griffon (Gyps himalayensis) in Upper Mustang, Nepal

Long-term conservation of the species requires the availability of their natural habitat along with all those factors that support their viability. Understanding the breeding success of vulture and different factors affecting it is important to line up species conservation, although very less is known about the reproductive and behavioral ecology of Himalayan griffon (Gyps himalayensis). Therefore, the present study was carried out in Upper Mustang areas of Nepal, a prime habitat for the species. For the determination of the factors influencing breeding success, exploratory research design was used. Identification of vulture’s nests was done by direct observation. Altogether 78 nests were identified with 41.02% breeding success with occupied nest as the primary unit. Almost all the productive nests were found in steep cliffs facing north direction. Nesting sites were located near water sources. Grazing and noise respectively have positive and negative impacts on the breeding success. Developmental activities like road construction, distribution of power lines is proven threat to vulture as per locals' perception and require development activities to be carried out with proper planning.

Urbanisation lowers great titParus majorbreeding success at multiple spatial scales

While numerous studies have reported negative effects of urbanisation on birds, few have examined the role of urban scale in influencing breeding success. Furthermore, many studies have relied on qualitative rather than quantitative assessments of urbanisation. This study sought to address these issues by testing the effects of urbanisation, measured at two spatial scales, on the breeding success of great titsParus major. A nested study design, incorporating over 400 nestboxes, was used in study sites across northern Belgium with a priori quantified degrees of urbanisation at both local and regional scales. All measured breeding parameters were found to vary at one or both spatial scales of urbanisation; in more urbanised areas great tits displayed advanced laying dates but lower breeding success compared to rural areas, with smaller clutch sizes, lower nestling masses and fewer fledglings per egg. Importantly, urbanisation effects were not limited to big cities as birds breeding in gardens or parks in small towns also had comparatively low success. We found that both regional‐ and local‐scale urbanisation had consistent significant effects on laying date, clutch size and nestling mass, while the number of fledglings per egg was negatively influenced by local‐scale urbanisation only. Results of this study therefore highlight the importance of utilising multiple spatial scales in analysing urbanisation effects, as well as the potential negative impact of local urbanisation on breeding success. This calls for further investigation into mechanisms driving urbanisation effects and how these may vary at different scales.

Ecosystem‐scale loss of grazing habitat impacted by abundance of dominant herbivores

AbstractGrazing lawns, patches of grazing‐tolerant plants with high nutrient value, provide important habitat for herbivores, and changes in abundance can impact herbivore populations. Grazing lawns are maintained in quality and quantity by repeated grazing and are a result of a positive feedback since the availability of grazing lawn can increase herbivore populations and increased herbivore populations can result in an increase in grazing lawn extent. We sampled aerial imagery from a long‐term dataset (>20 yr) at an internationally important breeding area for avian herbivores to model changes in grazing lawn abundance over time and identify the possible factors impacting those changes, including numbers of breeding birds, their primary predator, and spring phenology. Our data suggest that avian herbivores and their predators likely exert strong impacts on plant communities and may drive vegetation abundance. Decreases in the number of herbivore nests in our study coincided with an almost complete lack of grazing lawn in the mid‐2000s. Any factors dictating the amount of grazing lawn available for avian herbivores could strongly influence breeding success and the maximum size of these populations. Our results demonstrate the importance of studying complex interactions among predators, herbivores, and plants, and population moderation by both bottom‐up and top‐down processes.

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 PacificGavia pacifica, yellow‐billedG. adamsii, and red‐throated loonsG. stellataon 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.

Nest monitoring does not affect nesting success of Whinchats Saxicola rubetra

It is important to assess the effect that research activities may have on animals in the wild, especially when key parameters, such as breeding success, could potentially be influenced by observer activity. For birds, some studies have suggested that nest monitoring can increase the chances of nest failure due to predation, whereas others suggest that human nest visits may actually deter mammalian predators. Nest monitoring visits can also influence breeding success more indirectly by altering parental provisioning behaviour. Here, the influence of monitoring activities on nest success was examined in a ground‐nesting grassland bird, the Whinchat Saxicola rubetra. During the egg phase, a sample of nests were not visited between the initial finding event and the estimated hatching date; instead, the nest status was assessed at a distance. Daily survival rates (DSR) for these nests were compared with that of nests visited every 2 days. During the nestling phase, the effects of observer nest visits on parental provisioning behaviour were determined. Nest visits were found not to affect egg DSR significantly, and parental provisioning was disrupted for a maximum of 20 min (0.52% of the nestling period) following an observer visit. Given the variation in response to nest visits across species, we suggest that consideration should be given to observer impact in all studies where predation risk is high. Here, we illustrate a method for researchers to assess the impact of their nest visits to ensure they are not biasing estimates of breeding success.

Impact of mimicking natural dispersion on breeding success of captive North American Cheetahs (Acinonyx jubatus).

This paper examines the effects of transfer away from natal facility and littermate presence on cheetah breeding success in the AZA Species Survival Plan (SSP) population. Transfer and breeding history data for captive males and females were gathered from seven and four AZA SSP breeding facilities, respectively, to identify factors influencing breeding success. The results indicate that transfer history (p = 0.032), age at transfer (p = 0.013), and female littermate presence/absence (p = 0.04) was associated with breeding success, with females transferred away from their natal facility before sexual maturity and without littermates present accounting for the highest breeding success. Keeping males at their natal facility and/or removing them from their coalitions did not negatively affect their breeding success. Males appeared to demonstrate the same fecundity regardless of transfer history or coalition status, indicating that dispersal away from natal environment was not as critical for the breeding success of males compared with female cheetahs. These results highlight the significance of moving females away from their natal environment, as would occur in the wild, and separating them from their female littermates for optimization of breeding success in the ex situ population.

Do Arctic breeding geese track or overtake a green wave during spring migration?

Geese breeding in the Arctic have to do so in a short time-window while having sufficient body reserves. Hence, arrival time and body condition upon arrival largely influence breeding success. The green wave hypothesis posits that geese track a successively delayed spring flush of plant development on the way to their breeding sites. The green wave has been interpreted as representing either the onset of spring or the peak in nutrient biomass. However, geese tend to adopt a partial capital breeding strategy and might overtake the green wave to accomplish a timely arrival on the breeding site. To test the green wave hypothesis, we link the satellite-derived onset of spring and peak in nutrient biomass with the stopover schedule of individual Barnacle Geese. We find that geese track neither the onset of spring nor the peak in nutrient biomass. Rather, they arrive at the southernmost stopover site around the peak in nutrient biomass, and gradually overtake the green wave to match their arrival at the breeding site with the local onset of spring, thereby ensuring gosling benefit from the peak in nutrient biomass. Our approach for estimating plant development stages is critical in testing the migration strategies of migratory herbivores.

Nest site characteristics and breeding success of the red-backed shrike (Lanius collurio) in agricultural landscape in eastern Poland: Advantage of nesting close to buildings

One of the most important factors influencing breeding success in many bird species is predation. Nest site choice is one way of lowering the probability of such losses. In an agricultural landscape of eastern Poland, we examined the relationship between red-backed shrike (Lanius collurio) nest site characteristics, i.e., height above ground, concealment, and occurrence of thorns, and the risk of nest predation. We also considered the relationship with distance to potential predators, i.e., corvid nests, and the distance to buildings. Our results showed that only 1 environmental factor significantly influenced breeding success. Birds nesting closer to buildings achieved higher breeding success than those more distant from buildings. A positive correlation between date of first egg laying and distance from the nest to the buildings was also found. These results indicate that areas with human activities and buildings can created habitats that improve breeding success for some species. On the other hand, the growth of such habitats also contributes to decreasing availability of semi-natural areas for breeding and foraging for these species.

Simulating the responses of forest bird species to multi-use recreational trails

Although non-consumptive recreation can promote wildlife preservation and add socio-economic value to parks and nature reserves, such activities can have negative implications for wildlife. For sensitive species, recreation can lead to displacement, influence breeding success and reduce survival. Thus managing recreational activities by regulating visitor access, densities and frequency can effectively reduce human–wildlife interactions. In many instances, simulation modeling has been used as a management tool, as it allows the user to explore the impact of alternative park designs and management strategies on wildlife in a risk-free environment. Such exercises tend to focus on single species, generally a species of conservation concern, on which management decisions are based. As an alternative approach, we used a modeling simulation to compare the disturbance caused by different trail designs, trail use rates and the management of invasive vegetation (i.e., removal) on a forest community of breeding birds at a state park in Indiana, USA. Our multi-species approach revealed that an appropriate trail design for one species was not necessarily appropriate for another, even among species of concern. We therefore caution that management based on a single high profile species could have far-reaching implications on the local community. We also found that invasive vegetation removal did not have a cumulative influence on the recreational disturbance experienced by birds. This study demonstrates that by identifying and comparing the differences between individual species within a community, we gain valuable insights that can be used devise more resilient long-term management strategies that aim to preserve biodiversity.

Free housing for declining populations: Optimizing the provision of artificial breeding structures

The improvement of habitat quality and reproductive success through the implementation of artificial breeding structures is one of the most widespread in situ conservation strategies applied to the recovery of declining wildlife populations. Several past studies have monitored the use of artificial breeding structures in the wild, but virtually none of them have investigated which demographic and environmental factors actually determine their effectiveness in facilitating reproductive success. Therefore, the aim of the present study was to identify those factors influencing breeding success in artificial structures. With this purpose we surveyed a declining population of a keystone species of Mediterranean ecosystems, namely the European wild rabbit. In Doñana National Park, we sampled during the course of two years the breeding success of wild rabbits from 47 artificial warrens, experimentally provided under different demographic and environmental conditions. In order to determine the relative importance of such factors, we applied an AIC model selection procedure to alternative biological hypothesis groups, postulating that breeding success in artificial structures would primarily depend on population density, food availability and/or predator limitation. We found that the efficiency of artificial warrens in facilitating rabbit reproductive success can vary, with an increase associated with greater pasture availability. Predator limitation by fencing also positively affected rabbit reproduction, but only in combination with high pasture availability. On their own, fencing treatment and population reinforcements had low and null effectiveness facilitating reproduction, respectively, as well as entailing significant economic and biological costs. The best way to improve breeding success in artificial structures, therefore, was through their strategic placement in potential high-quality habitats, i.e. with suitable pasture availability. We suggest that vegetation management can effectively increase carrying capacity and consequently the target species’ reproductive success, especially in fast breeding species like the European wild rabbit. The provision of artificial breeding structures for conservation purposes may significantly benefit from the elaboration of concurrent experimental studies similar to the present research, which can help establish useful guidelines for optimizing future conservation efforts.

Long-acting neuroleptic use for reproductive management of non-domestic ungulates using the domestic goat (Capra hircus) as a model

Fluphenazine decanoate is a long-acting phenothiazine neuroleptic that attenuates the stress response and may be useful during intensive handling for reproductive procedures in non-domestic ungulates. However, phenothiazines are also associated with elevated serum prolactin, which can suppress fertility in some species. For this study, 10 female domestic goats were used as a model for non-domestic caprids to test effects of fluphenazine decanoate on serum cortisol and reproductive cyclicity following estrus synchronization. Two identical trials were conducted during the breeding season, employing a random crossover design. First, females underwent estrus synchronization using a 14-day treatment with progesterone (330 mg; CIDR). After 7 days of CIDR exposure, the treatment group (n = 5) received fluphenazine decanoate (1.0 mg/kg IM) and controls (n = 5) received an equivalent volume of 0.9% saline IM. At CIDR withdrawal (Day 14), animals received 125 mg cloprostenol sodium to lyse any luteal tissue and synchronize estrus. Blood was collected every 2 hr from 36 hr after CIDR withdrawal until 24 hr after standing estrus, or up to 5 days to monitor stress and reproductive hormones. Serum cortisol, prolactin, luteinizing hormone (LH) and progesterone concentrations were determined by enzyme immunoassay. While treatment with fluphenazine was associated with lower cortisol concentrations compared to controls (P = 0.001), 4 of the 10 treated animals experienced elevated serum prolactin, suppression of the LH surge and inhibition of ovulation. These findings suggest that long-acting neuroleptic drugs reduce the adrenal stress response, but may interfere with reproductive responses and negatively influence breeding success.

Factors influencing breeding success, ovarian cyclicity, and cub survival in zoo-managed tigers (Panthera tigris)

Understanding factors that influence reproduction and offspring survival in zoo populations is critical for management of threatened and endangered species. Examination of long-term data (1989–2011) compiled from the Association of Zoos and Aquarium's zoo-managed tiger breeding program provides the basis for a more thorough understanding of reproduction and scientifically based decisions for effective population management in this endangered felid. Biological and management-related factors that could influence tiger breeding success and cub survival were evaluated using logistic mixed models. Breeding success improved with female age until approximately age five, then declined thereafter. Experienced female breeders had greater breeding success than inexperienced females. Litter size was most predictive of cub survival, with average-sized litters (3–4 cubs) experiencing the highest proportional survival. Management-related factors, such as whether the breeding institution had a recent tiger litter and whether both animals were already located at the same institution, also influenced breeding success and cub survival. These results highlight the importance of institutional husbandry experience and the need to retain knowledge through staff turnovers to achieve optimal reproductive success. Using fecal estrogen data, frequency of ovarian cyclicity and mean cycle length did not differ by female age or parity; thus, lack of cyclicity and/or increased cycle duration are not likely explanations for declining breeding success with age. These results provide valuable reproductive information that should improve scientific management of zoo-based tiger populations.

Impact of predation by the black rat, rattus rattus, on the breeding success of cory’s shearwater, Calonectris diomedea, on Linosa island (Sicily, Italy)

Black Rat, Rattus rattus, is one of the most common species on Mediterranean islands; it is found on all of the large and medium-sized islands, and on many of the smallest ones as well (Perfetti et alii, 2001). On Linosa, the Black Rat was introduced by man and its density is not evaluable at present. Linosa island hosts the largest breeding colony of Cory’s Shearwater, Calonectris diomedea, in Italy (estimated at 10.000-15.000 pairs, Iapichino & Massa, 1989), and the second largest colony in the west-central Mediterranean (Granadeiro et alii, 1997). The aim of this work was to verify for the first time the limiting factors influencing breeding success in the Cory’s Shearwater breeding colony on the island of Linosa, with special attention to the impact of Black Rats.

Influence of spatial and temporal dynamics of agricultural practices on the lesser kestrel

Summary1. European agriculture is facing dramatic changes that are likely to have marked impacts on farmland biodiversity. There is an urgent need to develop land management strategies compatible with the conservation of biodiversity.2. We applied a spatially explicit behaviour‐based model to assess how farmland management and the pattern of events across the annual farming calendar influences the foraging decisions of lesser kestrelsFalco naumanniin a cereal steppe landscape. Moreover, we simulated the most likely scenarios of future agricultural changes to predict its impacts on lesser kestrel breeding success. Lesser kestrels have been the subject of serious conservation concern and constitute a good model species to judge impacts on farmland species more widely.3. Our results show that the location of cereal and fallow patches within a 2‐km radius of a kestrel colony influences the total food supply delivered to the nestlings, explaining the differences in breeding success between years and colonies. Furthermore, the particular sequence in which patches are harvested by farmers is also predicted to influence offspring survival.4. Agricultural intensification, simulated by increasing the proportion of cereal fields, is predicted to negatively influence breeding success. However, the field harvesting sequence can play an important role in alleviating the effects of the increased percentage of cereal, as demonstrated by the higher breeding success obtained when harvesting starts from patches farthest from the colonies. The replacement of cereal cultivation by low‐intensity grazed fallows would not be detrimental for kestrels.5. Synthesis and applications. Our results highlight the effectiveness of behaviour‐based models to evaluate the interacting effect of spatial and temporal dynamics of agricultural landscapes and predict the response of populations to environmental change. To optimize food availability for lesser kestrels, land managers should implement long rotational schemes with <60% of the area under extensive cereal cultivation in a 2‐km radius around colonies. Harvesting should start in the cereal patches farthest from colonies. Ideally, the predominant land use around colonies should be fallows. These outcomes illustrate how behaviour‐based models can be applied to identify specific management recommendations that would improve the effectiveness of agri‐environmental schemes, the most accepted tool for maintaining farmland landscapes.

Effect of habitat features on the breeding success of the blue penguin (Eudyptula minor) on the West Coast of New Zealand

We estimated the effect of selected habitat variables on burrow occupancy rate and breeding success of blue penguins in two regions of the West Coast of the South Island of New Zealand, South Westland (three colonies) and Buller (five colonies), in order to measure the impact of habitat changes on the West Coast blue penguin population. In both regions, habitat type did not appear to influence the breeding success of burrows and there was no significant difference in breeding success between colonial and isolated breeders in either region. Proximity to the hightide line and scrubline influenced the occupancy of nests in Buller but not in South Westland. Breeding success was apparently unrelated to the proximity of nests to the sea or to a road/track, suggesting that disturbance did not influence breeding success. These findings provide baseline data against which to measure the consequences of changes in breeding habitat and their impact on West Coast penguin populations, and guide the placement of artificial nest boxes.

Diet preference and breeding success in captive-bred Greater rheas (Rhea americana): a preliminary study

We conducted 2 consecutive experiments to verify whether adult captive Greater rheas (Rhea americana) could select diets differing in nutritional and energetic content, and to evaluate the effect of those diets on egg production and hatchability. From August to January, animals were offered four diets: processed feed for rheas (diet 1), diet 1 + soybean (diet 2), processed feed for chicken (diet 3), and diet 3 + soybean (diet 4). Rheas preferred the diets containing feed for chicken (diets 3 and 4, 179,67 ± 12.12 [S.E.] g/ind./day). Diet 2 was more consumed (95.67 ± 16.70 g/ind./day) than diet 1 (60.09 ± 11.31 g/ind./day), whereas preferences for feed for chicken did not vary with supplementation. Diet 1 and soybean-supplemented diets were consumed by males (113 ± 13.66 and 163.57 ± 13.33 g/ind./day, respectively) in a greater amount than by females (42.27 ± 8.61 and 96.72 ± 16.52 g/ind./day, respectively). Diet type did not affect egg production (43-63 eggs), but hatchability was 13% higher in eggs from females fed soybean-supplemented feed (diets 2 and 4), and those fed diet 2 produced more chicks. While diets 3 and 4 were apparently of lower nutrient quality, they provided more energy than those formulated with processed feed for rheas. Conversely, diet 2 seemed to be the most favourable for females during the reproductive season. The quality of diets provided to females would largely influence breeding success in captive Greater rheas.

Does Threat to the Nest Affect Incubation Rhythm in a Small Passerine?

Nest predation is a crucial factor influencing breeding success in birds. One possible way to protect nests is to modify parental activity in the vicinity of the nest. Here, we provide experimental evidence for an adjustment of incubation pattern during periods when there is an increased risk of nest predation in a small passerine. We compared the behaviour of incubating meadow pipit (Anthus pratensis) females during presentations of stuffed dummies of a nest predator (the magpie Pica pica) and a harmless intruder (the crossbill Loxia curvirostra) and during an undisturbed control incubation period. Females significantly decreased their activity in the presence of the nest predator. Specifically, after being flushed out, they returned to the nest later and moved to and from the nest less than when the harmless intruder was present. These results document the ability of birds to assess the nest predation risk and adjust their appropriate incubation strategy.

Breeding Success of Western Reef Heron in Hara Biosphere Reserve, Persian Gulf

Abstract. Breeding success of the Arabian/Indian race of the Western Reef Heron Egretta gularis schistacea was studied in the Hara Biosphere Reserve, Persian Gulf, during 2008 and 2009, with 103 and 137 nests studied, respectively. Marked nests were checked at least twice a week to note egg-laying date, clutch size, brood size, egg loss and chick mortality. Also, hatching and breeding success were estimated. Egg-laying was from 21 March to 17 April in 2008 and from 28 March to 28 April in 2009. Mean clutch size in the two years combined was 3.4 ± 0.05 and significantly greater in 2009 (3.5 ± 0.07) than 2008 (3.2 ± 0.07). Mean brood size was 2.0 ± 0.1 for all clutches and was greater in 2008. The internal diameter of nests, the height of nests from the ground and the distance of nests from the mangrove forest border were important factors influencing breeding success. The percentage of successful nests varied significantly between the two years (80% in 2008 and 51% in 2009). Overall, approximately 64% of n...