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(Received 21 February 2012; accepted in revised form 4 July 2012) ABSTRACT. A detailed understanding of the processes and interactions within biological communities is needed to describe and predict the [...]

Abstract: We evaluated covariation between Chinook salmon (Oncorhynchus tshawytscha) abundance and seabird breeding success in central California, USA, and compared potential forecasts to predictive models based on jack (2-year-old male) [...]

The nesting ecology of breeding pairs of the Western Gull x Glaucous-winged Gull (Larus occidentalis x glaucescens) hybrid complex was investigated at two locations in coastal Washington. In Grays Harbor, breeding performance (clutch size, hatching and fledging success) was highest in vegetated habitat where nests were most dense and where natural screens blocked the nearest neighbor. Egg loss, presumably from gull predators, was common except in areas of dense vegetation. At Tatoosh Island, egg loss was rare, and breeding performance was similar in vegetated and rock habitats. To test if physical structure around open-area nests influenced egg loss in Grays Harbor, predator-exclusion fences were erected around nests on a sandbar island lacking vegetation. Excluding predators reduced egg loss and increased hatching success relative to nests with adjacent natural screens (driftwood logs >30 cm tall) or nests lacking natural screens. Pairs that nest in habitats with adequate habitat structure appear to benefit in terms of lower egg loss and higher nesting success, especially in Grays Harbor. Increasing structure around individual nests may increase breeding success of gulls or other seabirds that experience extensive nest predation. Key words: Breeding success, egg loss, Glaucous-winged Gull, habitat, Larus glaucescens, L. occidentalis, Western Gull.

Understanding the mechanisms causing temporal variability in demographic parameters is essential to understanding fluctuations in populations. As part of a long-term demographic study, we evaluated influence of climate on Mexican Spotted Owl (Strix occidentalis lucida) annual survival and reproduction in two study areas, one in Arizona and one in New Mexico. Spotted Owl survival in New Mexico and reproductive output in both study areas were positively related to total amounts of precipitation from the previous year, previous winter, or monsoon season. For both study areas, temporal process variation in reproductive output (CV[R] = 51.2 and 75.2% for Arizona and New Mexico, respectively) was greater than that for survival (CV[[phi]] = 12.9 and 7.1% for Arizona and New Mexico, respectively). Precipitation from the previous year explained 73% of [[sigma].sup.2.sub.temporal] reproductive output for Arizona owls and precipitation from the previous monsoon explained 42% of [[sigma].sup.2.sub.temporal] in reproductive output for New Mexico owls. Precipitation from the previous monsoon season explained 53% of [[sigma].sup.2.sub.temporal] in Arizona owl survival and precipitation from the previous winter explained 56% of [[sigma].sup.2.sub.temporal] in New Mexico owl survival. The two populations of Spotted Owls we studied appeared to have the same life-history strategy hypothesized for a population of Northern Spotted Owls (S. o. caurina), although the Mexican subspecies apparently responded quite differently to climatic variation. Received 6 February 2001, accepted 29 October 2001.

ABSTRACT--The association patterns between breeding bird diversity and amount of different land cover types at five spatial scales were analyzed. Breeding bird surveys were conducted at 2,021 randomly selected roadside [...]

The population fecundity index for Metapenaeus ensis is higher than that for M. endeavouri with significant variation in the latter's monthly fecundity index as determined by the spawning patterns. Seasonal data indicate that offshore movements of the mature female prawns of the two species occur at different times.

Research on Israeli populations of Asiatic wild ass Equus hemionus indicates that female use of multiple male territories and rapid male turnover are necessary to alleviate population decreases. Territory was also found to be a significant factor, as size of territory was found to affect breeding strategies.

We studied between-year dispersal of adult females within a population of cooperatively breeding Red-cockaded Woodpeckers (Picoides borealis) in the Sandhills of North Carolina, using data collected between 1980 and 1995. We tested four hypotheses about the cause of breeding dispersal: inbreeding avoidance, mate choice, site choice, and social constraints. In addition, we assessed relationships among age, reproductive failure, and breeding dispersal, and we estimated cost of breeding dispersal by plotting mortality against dispersal rate as a function of circumstance. Breeding dispersal in the population that we studied is associated with multiple factors. Inbreeding avoidance influences dispersal of females whose sons inherit their natal territories. Mate choice influences dispersal of females whose mates have died; these females acquire older, higher quality mates by dispersing. In this study, there was no clear relationship between site choice and breeding dispersal. Social constraints do not appear to affect breeding dispersal in this population: no evidence was found to suggest that dispersal is associated with female-female competition, within-group competition for resources, or reproductive competition between mothers and helper sons. The effect of reproductive failure on breeding dispersal changes with female age. Reproductive failure is associated with breeding dispersal in young females only (those Key words: breeding dispersal; cooperative breeding; cost of dispersal; inbreeding avoidance; mate choice; North Carolina; Picoides borealis; Red-cockaded Woodpecker; site choice; social constraints.

Tropical wet forests are commonly perceived as stable and constant environments. However, many rain forest organisms reproduce seasonally. To understand the proximate regulation of life history events in tropical organisms, we asked three questions: (1) How predictable are seasonal changes in the tropical rain forest? (2) Can tropical organisms anticipate environmental seasonality, despite the presumed lack of long-term environmental cues in near-equatorial areas? (3) What environmental cues can tropical organisms use? We studied Spotted Antbirds, monogamous understory insectivores, which started breeding in Panama (9 degrees N) in May (wet season) and continued until September/October. Breeding patterns were consistent between years, indicating that tropical seasons were as predictable for Spotted Antbirds (predictability 70%) as they are for many north temperate birds. Individual Spotted Antbirds shut down reproductive capacity (i.e., decreased gonad size) from October until February. In March, during the height of the dry season and about six weeks ahead of the wet season, gonads started to grow again. The growth rate of gonads was influenced by the amount of rainfall, which has been shown to correlate with food abundance. Gonad growth was paralleled by changes in luteinizing hormone, but not in testosterone, which remained at very low plasma levels year-round. The latter contrasts with the pattern, for most migratory temperate-zone birds. Seasonal changes in reproductive activity correlated strongly with changes in the tropical photoperiod, but weakly with light intensity and rainfall, and not with temperature. Thus, Spotted Antbirds likely anticipated rain forest seasonality using long-term cues (tropical photoperiod) and fine-tuned their reproductive activities using short-term cues (food/rainfall). The use of long-term environmental information could apply to most vertebrate species that live in the tropics. Key words: environmental cues; food supply; gonad growth; hormonal changes; Hylophylax n. naevioides; photoperiod; predictability of tropical seasons; rainfall; rain forest; seasonal reproduction; Spotted Antbird; tropics.

We studied the effects of heavy and prolonged rainfall associated with four El Nino events on the reproduction of Darwin's finches on the Galapagos island of Daphne Major. Rainfall varied in the El Nino years from 195 mm to 1359 mm, exceeding the maximum in the other years by 40% to 1000%. Two species were studied: Geospiza fortis, Medium Ground Finch, and G. scandens, Cactus Finch. Almost all eggs, nestlings, and fledglings produced by banded females were recorded in the El Nino years of 1983, 1987, 1991, and 1998. Finch production in these years was compared with production in 10 other years of breeding in the period 1976-1990; there was no breeding in three drought years, 1985, 1988, and 1989. Breeding differed in the two sets of years in several ways. More broods were produced in EL Nino years than in non-El Nino years (maximum 10 clutches per female vs. five clutches), the period of breeding was longer (maximum eight months vs. four), average clutch sizes (range 2-6 eggs) were distinctly larger (four vs. three), and average egg and fledgling production per female was larger by a factor of four. The two species differed in some features of breeding, but differences were minor in comparison with the marked seasonal and annual variation. Finch production varied among El Nino years, being greatest in the year of most rain over the longest period (1983), and least in the next wettest year (1998). The surprisingly low production in 1998 is attributed in part to interactions with other finches, and in part to exceptionally high temperatures. Temperature, although postively correlated with rainfall, had an independent negative effect upon hatching and overall breeding success of G. fortis. Breeding by both species in the year of birth (hatch) occurred in two El Nino years with the most extended wet seasons: 1983 and 1987. Young breeders had lower clutch sizes and breeding success than did contemporaneously breeding older birds. Observations in different El Nino years show that finch population responses to major climatic perturbations such as elevated rainfall vary for two major reasons: the perturbations themselves vary in strength and duration, and responses to them are determined, in part, by preceding conditions. Those preceding conditions, in turn, are determined by whether drought or normal conditions precede the perturbation, and on the interval since the previous El Nino event. Thus, perturbations of natural systems can be fully understood only in a broad temporal context. Key words: breeding success; Darwin's finches; El Nino; food supply; Galdpagos; Geospiza fortis; Geospiza scandens.

Results suggest that using stable-carbon and hydrogen isotope ratios are a reliable means of determining blackbird breeding origins along a latitudinal transect from Louisiana to Saskatchewan. The method was applied to the outer primary feathers, which determined dietary intake of carbon and precipitation exposure.

Results suggest that south-to-north parallel ecological gradients influence sexual selection on song and concomitant divergence in song structure among the northern populations of avian ring species.

Small mammals in the tropics and subtropics usually rely opportunistically on favorable environmental conditions for breeding rather than base their breeding decision on prediction from photoperiodic cues as most high-latitude species do. Species producing precocial young may be more likely to reproduce aseasonally than species with altricial young. For female wild guinea pigs (Cavia aperea) from Argentina (35 degrees S) that produce extremely precocial young, these hypotheses would predict moderate responsiveness of female reproduction to photoperiod. These predictions were tested in a series of laboratory experiments. Guinea pigs reproduced aseasonally when kept under natural photoperiod and temperatures at Bielefeld (52 degrees 01'N, 8 degrees 32'E). When given short days (9L:15D) and long days (14L:10D) under indoor temperature conditions (20-23 degrees C), no effect of photoperiod on female reproduction was noted. A shift from long day length (14L: 10D) to short day length (9L: 15D) did not stop reproduction. Increasing energy expenditure for thermoregulation at low temperature (5 degrees C) under long-day (14L: 10D) conditions also did not inhibit reproduction. Wild guinea pigs thus reproduce throughout the year without respect to photoperiod as long as food and temperature conditions allow reproduction. Key words: Cavia aperea, opportunistic breeding, photoperiod, precociality, temperature, wild guinea pig

Population structure and reproductive ecology of the burrowing ghost shrimp Callianassa filholi Milne-Edwards, 1878 were studied in populations along a latitudinal gradient throughout New Zealand during the breeding season. Size-frequency distributions revealed unimodal populations, with predominantly sexually mature shrimp. All populations showed an unbiased sex-ratio, and there appeared to be no significant difference in size (carapace length, CL) between sexes. At the same time, CL and size at maturity differed significantly between populations; however, a general increase in sizes from north to south was not consistent throughout the latitudinal range studied. The timing of the breeding cycle differed significantly between populations, and breeding started earlier in southern populations. Number of embryos (fecundity) increased linearly with female CL at each location, but rates differed significantly between populations. Embryo size was not related to number of embryos, and the former increased significantly with latitude. With the exception of embryo size, observed differences in body size/size at maturity and reproductive timing between C. filholi populations are thought to be determined by food availability rather than temperature. Thus, further study is suggested on these aspects of thalassinid reproductive biology.

Research on Northern Flicker mate selection was conducted according to color factored with other categories, including bill length, wing length, and tail length. Mate selection was correlated to overall color, nape color and shape, and moustache color.

White-crowned Pigeons (Columba leucocephata) varied their timing of breeding and nesting intensity in response to variation in production of the four most important fruit species in their breeding-season diet in the upper Florida Keys. From 1988 through 1990, we monitored fruit production year-round in five habitats in which pigeons foraged and monitored all pigeon nests along two transects on Middle Butternut Key. Annually, pigeon breeding was positively correlated with summer rains and with the peak in overall fruit production. However, within the breeding season, only the availability of Metopium toxiferum was positively correlated with rainfall and the number of new clutches initiated. Both the timing and magnitude of breeding varied annually. In 1988, when Metopium was more available, more pigeons nested, the nesting season started earlier and lasted longer, and a large peak in nesting occurred when Metopium fruit ripened. During 1989 and 1990, when the relative availability of Metopium was lower, fewer pigeons nested, the nesting season was shorter, and the seasonal peak in nesting associated with Metopium fruit was reduced or absent. Nesting patterns did not appear to vary with changes in the relative availability of other fruits. White-crowned Pigeons appear to prefer Metopium fruits to other species. Because pigeons do not supplement nestling diets with arthropods, but augment their diets with protein-rich crop milk, they may depend on lipid-rich fruits such as Metopium to provide the energy for breeding and crop-milk production. Metopium fruit production may be influenced by rainfall and climatic conditions, both of which may vary spatially within the range of White-crowned Pigeons in Florida. Evidence that pigeons shift foraging sites when Metopium availability varies emphasizes the need to preserve large tracts of seasonal deciduous forest in the Keys and to protect Metopium trees in suburban areas where they are removed because they cause contact dermatitis in humans.

An evaluation is presented on breeding related individuals to alleviate inbreeding depression in wildlife conservation. It is posited that this process results only in a temporal improvement in fitness, and is not reliable due to organism response to environmental pressures.

An early summer breeding hiatus in wild populations of white-footed mice (Peromyscus leucopus noveboracensis) in eastern Virginia has been well documented. This report explores the question of the age of the reproductively inhibited animals and demonstrates that mice reproductively suppressed during the hiatus period were not merely young-of-the-year who had not reached sexual maturity but were adults, many of which were known to be reproductive before the hiatus period. Further, animals known to be adults for an average of >2 months when necropsied during the hiatus period had significantly smaller testes, seminal vesicles, and ovaries than adults with similar histories, captured, and necropsied during other reproductive periods of the year. Key words: Perornyscus, population, reproductive hiatus

The field metabolic rate (FMR) of nesting Northern Fulmars (Fulmarus glacialis) was measured using the doubly labeled water technique. Although some labeled Northern Fulmars showed marked differences in behavior compared to controls, FMR did not change correspondingly. At-sea FMR averaged 1444 kJ/d, equivalent to 4.5 x basal metabolic rate (BMR). As a multiple of BMR it was independent of sex, wing length, body mass, mass change, and duration of the period at sea, but was strongly dependent on wind speed, being higher during slack winds. There was also a trend for higher wingbeat frequency at winds too low for sustained dynamic soaring. The high energetic cost of flapping flight during windless conditions may explain patterns of nest attendance: in particular, why nest site attendance by Northern Fulmars in winter is greater during calm weather. Lack of wind might limit the breeding range of this species and other Procellariiformes with high flapping-flight costs. Key words: breeding distribution; procellariiform; energetics; flight characteristics; foraging; labeled water; Northern Fulmar; seabird; weather effects., INTRODUCTION The Northern Fulmar (Fulmarus glacialis) has been identified as one of the main avian consumers of sand-eels (Ammodytes marinus) in Shetland (Furness 1990) and in the North Sea (Anonymous [...]

Studies of life history evolution, as well as much of life history theory, have typically focused on "hard" components of life histories; phenotypic characteristics that can be readily observed, quantified, and ultimately, connected rather directly to fitness. Typical of these are propagule size, propagule number, and age and size at maturity. What is largely missing from the study of life history evolution is consideration of the role of behavior, principally female oviposition site choice, in the evolution of life histories. For oviparous organisms, natural selection cannot produce locally optimized "hard" components of life history phenotypes without a consistent environmental context (whether invariant or variable); in a variable environment, that consistent environmental context can be most effectively provided by interactive oviposition site choice. I present a model of selection on oviposition site choice in the context of the evolution of "hard" components of life history phenotypes, along with some experimental data illustrating oviposition site choice in response to predators. The model and data are then related to the overall question of the role of oviposition site choice in life history evolution. The conclusion is that oviposition site choice must be under equally strong selection with egg size, egg number and the other hard components of life histories in order to generate and optimize locally adapted or ecologically specialized life history phenotypes, and must therefore, play a significant role in the evolution of life histories.

The nocturnal behavior of Trumpeter Swans breeding in Wyoming and Idaho were examined using sophisticated night-vision equipment. Observations confirmed that breeding Trumpeter Swans remained active at night, although the degree of activity varied as the breeding season progressed. Results also suggested that nocturnal behavior was affected by environmental factors, such as the availability of food resources on breeding grounds and ambient temperature.

Facultative paedomorphosis in salamanders is a plastic trait that may represent an adaptation to fluctuating environmental conditions. I compared the timing of reproduction in paedomorphic and terrestrial-morph Ambystoma talpoideum at the same pond. Paedomorphic adults laid eggs approximately 6 wk earlier than terrestrial morphs. Early egg-laying and subsequent growth of hatchlings resulted in a significant size advantage for larvae from paedomorphic parents at the time that terrestrial-morph eggs hatched. These observations suggest that, under certain environmental conditions, facultative paedomorphosis is advantageous.

A population of adders (Vipera berus) in southern Sweden were studied from 1984-90 to determine whether whether there is temporal variability exists in selective forces, and whether alternative reproductive tactics exist as a consequence of variable selective forces. The results showedthat in adders, intensity of sexual selection for dominance over rival males varied considerably in different years, and depended on the number of reproducing males and females in the population. The implications for findings on the effects of sexual selection on the evolution of mating systems and sexual dimorphism based on short-term studies were discussed.

A temporal-threshold model for polygynous mating (TMPM) is presented. The model is an extension of the polygyny-threshold model and shows how polygyny costs and cyclical environments affect the temporal patterns of reproduction in polygynous animals. The mating system of the African elephant (Loxodonta africana) and the spawning behavior of the Hawaiian Potter's angelfish (Centropyge potteri) were seen to correspond to the predictions of the TMPM, which is applicable only to species where females have limited access to available males.

The primary purpose of these studies was to determine whether photoperiodic signals could influence seasonal egg-laying behavior in the marine mollusk, Aplysia californica. Egg-laying behavior was monitored from groups of animals that were collected at four times of year and maintained in different temperature and photoperiodic conditions in the laboratory. Animals that were obtained in autumn and kept in warm water laid eggs more frequently than those in cold water, regardless of photoperiod. Furthermore, animals maintained on short days and warm water laid eggs more frequently than those on long days and warm water. Animals in cold water showed little to no egg laying, and a photoperiodic response was not evident. Animals that were collected in either winter or spring and maintained in warm water showed little or no spontaneous egg laying throughout the study, regardless of photoperiod. As with the autumn animals, Aplysia individuals obtained in summer and kept on short days and warm water laid eggs more frequently than those kept on long days and warm water. These results provide the first evidence that the reproductive system of A. californica is responsive to photoperiod. Overall, the data suggest that warm water is permissive for egg laying, and that short days can further stimulate this behavior. However, there is a strong inhibition of spontaneous egg laying during the winter and spring, which neither warm water nor short photoperiod can overcome. The role of the eyes in mediating the photoperiodic response was also investigated. A control group of intact animals kept on short days laid eggs more frequently than those on long days, but this photoperiodic response was not evident in eyeless animal. These results suggest that the eyes play a role in mediating the effects of photoperiod on egg laying behavior.

SYNOPSIS. Comparative ethological studies of closely related species can place into clear perspective the functions of behavioral traits as species diverge and adapt to different environments. In this paper we contrast the reproductive behavior of species within two crustacean groups: the mantis shrimps (stomatopods) and the fiddler crabs (genus Uca). For the stomatopods, we identify probable selective relationships between features of species' ecology and their mating systems. Population density, the kind and availability of shelters in which these shrimps live, the intensity of predation and spawning cycles all play important roles in molding reproductive behavior in this group. Associations between the ecology and mating systems of fiddler crabs have been discussed recently elsewhere. Here we focus on a comparative analysis of sexual communication in these crabs. A study of competitive courtship signaling and mate choice in the fiddler crab Uca beebei has shown that certain male courtship signals are highly attractive probably because they exploit female sensory-response systems that have been molded by selection for escape from predators. Interspecific comparison of male courtship displays and the responses of females to these displays suggest that sensory exploitation may play an important role in the evolution of sexual signals in the genus. Comparative studies have advanced our understanding of how natural and sexual selection affect the reproductive behavior of both stomatopods and fiddler crabs.

I examined the effect of frequent visits to barn owl (Tyto alba) nests by comparing nests subject to regular inspection from before laying to fledging with nests that were visited only immediately before fledging. I found no differences in the mean number of young fledged or in the mass of young at fledging. Nest visits did not encourage birds to change their nest sites in subsequent years. No difference in breeding performance was found between pairs that carried tail-mounted radio transmitters and pairs that did not.

Rock squirrels (Spermophilus) variegatus) were studied from July 1983 to June 1987 in an oak (Quercus sp.) savanna in southeastern Arizona. Adult males had testes in serotal position from late March until at least early July. Estrous females were observed from 15 May (the earliest that summer research begain in any year) to 16 June. Lactating adult females were observed from early June to early October, and, depending upon the year, the percentage of lactating adult femals peaked from early July to late August. The percentage of adult femals notlactating during the peack lactation period (16 June-15 September) ranged from 20 to 33% during a particular year. Yearling males had scrotal tests, and some (56%) yearling females lactated. Mating occurred from mid-April to early July. The mating period lasted approximately 9 weeks, and the timing of the mating period was associated closely with heavy summer rains, as juveniles first emerged shortly after the beginning of the rains and the concomitant increase in production of vegetation. Compared to many other ground-dwelling squirrels, rock squirrels in southeastern Arizona had a long breeding season that seemed to be associated with the extent of the summer rainy season and to the absence of a relatively early, cold winter that limits aboveground activity of many North American ground squirrels during autumn and winter.

Dispersal dimorphisms, in which both flight-capable and flightless adults occur in the same species, are commonplace in insects. Such dimorphisms are seen as reflecting a balance between the benefits and costs of flight and wing reduction or loss. In heterogeneous habitats, theory predicts that fitness trade-offs can favor the evolution of a dispersal dimorphism in which both flight-capable and flightless morphs are retained in the same population. Despite the wealth of theory, however, there has never been an explicit field assessment of how habitat heterogeneity directly influences the reproductive success of the flight-capable and flightless wing forms of an insect species. The objective of this research was to investigate how variation in habitat heterogeneity (vegetation structure) and female density influence mate location and thus the potential for reproductive success by the male wing forms of a salt marsh inhabiting insect, the planthopper Prokelisia dolus. By placing unmated females in the field at different densities and in sparse and contiguous vegetation, we were able to compare the ability of male wing forms to locate stationary mates. Our data show that both vegetation structure and female density differentially influenced the ability of the male wing forms to locate mates. Flight-capable males located females and acquired matings far more frequently in sparse vegetation, whereas flightless males discovered females more often in contiguous vegetation. Flight-capable males located females more effectively at low female densities, whereas flightless males discovered females more efficiently at higher female densities. Thus, natural variation in vegetation structure and female density are two important factors which combine to influence the mating success of each male wing form. We conclude that habitat heterogeneity in concert with the known reproductive penalties imposed by flight capability (reduced siring ability) interact to favor the persistence of the dispersal polymorphism in males of this planthopper species. Key words: dispersal; flightlessness; mate location; planthopper; Prokelisia dolus; trade-off between flight capability and reproduction; wing polymorphism.