Patterns Of Breeding Activity Research Articles

Rapid plastic breeding response to rain matches peak prey abundance in a tropical savanna bird.

Changes in climate are shifting the timing of life cycle events in the natural world. Compared to northern temperate areas, these effects are relatively poorly understood in tropical and southern regions, where there is limited information on how timing of breeding and food availability are affected by climatic factors, and where patterns of breeding activity are more unpredictable within and between years. Combining a new statistical modelling approach with 5years of continuous individual-based monitoring of a monsoonal tropical insectivorous bird, we quantified (a) the proximate climatic drivers at two trophic levels: timing of breeding and abundance of arthropod prey; (b) the effect of climate variation on reproductive output and (c) the role of individual plasticity. Rainfall was identified as the main determinant of phenology at both trophic levels. Throughout the year, likelihood of egg laying increased very rapidly in response to even small amounts of rain during the preceding 0-3weeks. Adult body mass and male sperm storage also increased rapidly after rain, suggesting high breeding preparedness. Additionally, females were flexible, since they were more likely to nest whether their previous attempt was longer ago and unsuccessful. Arthropod abundance also increased after rainfall, but more slowly, with a peak around 10weeks. Therefore, the peak food availability coincided with the presence of dependent fledglings. Fitness benefits of nesting after more rain appeared to be linked to offspring quantity rather than quality: nest attempts following higher rainfall produced larger clutches, but showed no improvement in nestling mass or relative fledging success. The response of clutch size to rainfall was plastic, since repeated sampling showed that individual females laid larger clutches after more rain, possibly mediated by improved body mass. Rapid, individually flexible breeding in response to rainfall and slower increase in arthropod abundance also as a response to rainfall, might buffer insectivorous species living in tropical seasonal environments from climate change-induced phenological trophic mismatches.

DISTRIBUTION PATTERNS OF WOOD FROGS (RANA SYLVATICA) IN DENALI NATIONAL PARK

The objectives of this study were to document the presence of breeding populations of wood frogs (Rana sylvatica) in Denali National Park and Preserve and to examine landscape and habitat factors associated with population distribution. Surveys were conducted within 41 circular plots, each 1 km in diameter. All lentic sites were surveyed within each 1-km plot to determine the presence of wood frogs and to collect habitat data. Of the 219 sites surveyed, breeding activity (the presence of eggs or larvae) was observed at 98 sites (45%). Larger and less isolated sites had a higher incidence of observed breeding activity. Also, breeding activity was more frequently observed at sites with more emergent vegetation and more woody vegetation in the riparian zone, especially riparian zones with alder and spruce. Breeding activity was less often observed at deeper sites, sites with a permanent stream connection, sites where sphagnum (peat) dominated the substrate, and sites with beaver activity. A multifactor habitat model was developed using classification trees and parsimonious model selection protocol. The final model identified proportion of woody vegetation in the riparian zone, dominant substrate type, presence of alder in the riparian zone, and observed beaver activity as 4 habitat factors that accurately described breeding activity patterns in the study area. The results show that breeding populations of wood frogs saturate the landscape in the Wonder Lake region with nearly half of the lentic habitat sites being used by wood frogs. The majority of the sites were well into the shrubby tundra and >1000 m from boreal forest, suggesting that wood frogs in Alaska may frequent non-canopied areas at higher elevations as long as shrubby vegetation is present in riparian areas.

Breeding activity patterns, reproductive modes, and habitat use by anurans (Amphibia) in a seasonal environment in the Pantanal, Brazil

AbstractAnnual patterns of breeding activity, reproductive modes, and habitat use are described for a frog community in a seasonal environment, in the southern Pantanal, Mato Grosso do Sul, Brazil. Data were collected monthly between January 1995 and December 1998. A total of 24 species from four families; Bufonidae (3 species), Hylidae (10 species), Leptodactylidae (9 species), and Microhylidae (2 species) were registered. Three reproductive activity patterns are recognized among these species: continuous, explosive, and prolonged; 50% of the species were explosive breeders. Seasonal pattern of reproduction was verified for three analyzed years (1995-1997); most species reproduced during the rainy season (Nov-Jan). The reproduction was aseasonal in 1998; unexpected rains in the dry season lead to an unusual breeding activity. Five reproductive modes were noted — 62.5% of the species have the generalized aquatic mode, and 33.3% deposit eggs embedded in foam nests. Many species used the same sites for reproduction, although temporal partitioning and calling site segregation was observed. The occurrence of many species that exhibit explosive breeding early in the rainy season is common in seasonal and open environments with variable and unpredictable rainfall, as is the case in the Pantanal.

Breeding Biology and Productivity of Florida's Crested Caracaras

I studied the breeding biology of Crested Caracaras (Caracara plancus) in south-central Florida from 1994 through 1996. Reproductive activity was monitored year-round on 30, 48, and 55 territories, respectively. Pairs remained on breeding territories throughout the year and exhibited strong fidelity to the nest site between years; however, annual turnover rate among known breeding individuals was approximately 18%. Territorial occupancy and breeding rates on known occupied territories averaged 95% and 98%, respectively. Observed patterns of breeding activity and nesting success suggested a link between reproduction and precipitation. Active nesis were found from September through June, but most nesting activity corresponded with the dry season. November through April. Egg laying in many pairs occurred following an abrupt decline in precipitation in the fall each year. The overall probability of a nest producing at least one independent young was 72%; however, nest success varied throughout the breeding season, being lowest and most variable for early- and late-season nests. Based on 98 nests with complete records, mean clutch size was 2.23 eggs, 61.2% of nestlings fledged successfully, and 48.4% of all eggs laid resulted in independent young. Clutches of three produced the most independent young per breeding attempt in all years. Annual population productivity was enhanced because pairs made more than one nesting attempt per breeding season, either by renesting following an early season failure or by producing second broods. Clutch size, probability of nest success, probability of renesting, and number of fledglings produced per attempt all declined as the breeding season progressed. Mortality factors included weather, predation, chicks falling out of nests, and vehicle collisions with fledglings. Environmental variability may influence spatial and temporal variation in timing of reproduction and nesting success of Crested Caracaras in Florida.

Improved procedures for maintaining and breeding the short-tailed fruit bat (Carollia perspicillata) in a laboratory setting.

Improved methods have been developed for maintaining and breeding the neotropical short-tailed fruit bat, Carollia perspicillata, in an easily-reproduced, laboratory setting. Bipartite, all-metal cages have been designed which permit efficient, non-injurious handling of the animals. Also, a fruit-based liquid diet, which is simple and inexpensive to prepare, has been formulated from readily-available canned and powdered components. When efforts were initiated to breed wild-caught animals at 3-6 months after capture, this progressed slowly in most (but not all) cages. Breeding took place more rapidly when the bats had been in captivity for 11-24 months. Most females (122/144, 84.7%) then bred within 30 days of the introduction of a stud male, and the overall conception rate was 94.3% in those females which bred. This pattern of breeding activity, evidence that this bat is a spontaneous ovulator, and observed intervals between successive breeding periods (apparently representing much or all of non-pregnant cycles) in some individuals suggest that the cycle length in many of these bats probably falls between 20 and 30 days. Analysis of the breeding data also showed that certain patterns of breeding activity were frequently associated with a failure of females to establish ongoing pregnancies. Most laboratory-bred females (69/81) that were permitted to carry their pregnancies to term did so and successfully reared their young. The laboratory-reared young have generally exhibited excellent body condition, and many have proved to be fertile. The bats were found to exhibit a post-partum oestrus, which in nearly all cases (35/36) was fertile. The interval between the discovery of a new baby and the detection of a sperm-positive vaginal aspirate varied between 3-10 days, but most frequently was 3-6 days. Females which aborted non-term fetuses also had a post-partum oestrus with similar timing. These findings indicate that the short-tailed fruit bat, which is widely abundant in the lowland tropics of the New World, can be successfully maintained under controlled conditions, in cages of modest dimensions, for research purposes.