Nest Depredation Research Articles

Snakes are Important Nest Predators of Dickcissels in an Agricultural Landscape

Abstract We used video cameras to monitor 33 Dickcissel (Spiza americana) nests during 2003–2004 in the highly-fragmented, agricultural ecosystem of eastern Nebraska and western Iowa. Nine nests fledged young, 20 were completely depredated, three were partially depredated, and one was abandoned due to ants. Nine snakes, six small mammals, six common raccoons (Procyon lotor), two Brown-headed Cowbirds (Molothrus ater), and one American mink (Neovison vison) were documented as nest predators. These results suggest a diversity of predators is responsible for depredation of Dickcissel nests with snake predation being an important cause of nest failure.

Predators and nest success of Sky Larks Alauda arvensis in large arable fields in the Czech Republic

Capsule Nest failure owing to a range of predators was high, but the level and specificity of nest depredation cannot be generalised. Aims To determine fates and predators of Sky Lark nests in conventionally managed arable fields in the Czech Republic. Methods Sky Lark nests in large fields (mainly Maize, Sugar Beet and Opium Poppy) were monitored by means of continuous video surveillance. Results Primary nest fates of 42 active nests were fledging (13), depredation (22), desertion (5), nestling death (1), and flooding (1). The overall nest success (Mayfield estimate) was 17% (all mortality factors considered) or 27% (only depredation). Depredation events were caused by Marsh Harrier Circus aeruginosus (11), Hooded Crow Corvus cornix (4), Stone Marten Martes foina (3), Montagu’s Harrier Circus pygargus (2), Red Fox Vulpes vulpes (2), Hedgehog Erinaceus sp. (2) and Eurasian Jackdaw Corvus monedula (1). Successful nests were only slightly more away from field edge than depredated nests; nests taken by birds tended to be closer to field edge than those depredated by mammals. The possible reasons for the absence of a clear edge effect include comparatively large field parcels (about 50 ha) and location of nests far from field edge (median = 195 m). Conclusion Nest survival and composition of nest predators are site‐specific and contingent upon the study method and may not be simply generalised.

Climate and predation dominate juvenile and adult recruitment in a turtle with temperature‐dependent sex determination

Conditions experienced early in life can influence phenotypes in ecologically important ways, as exemplified by organisms with environmental sex determination. For organisms with temperature-dependent sex determination (TSD), variation in nest temperatures induces phenotypic variation that could impact population growth rates. In environments that vary over space and time, how does this variation influence key demographic parameters (cohort sex ratio and hatchling recruitment) in early life stages of populations exhibiting TSD? We leverage a 17-year data set on a population of painted turtles, Chrysemys picta, to investigate how spatial variation in nest vegetation cover and temporal variation in climate influence early life-history demography. We found that spatial variation in nest cover strongly influenced nest temperature and sex ratio, but was not correlated with clutch size, nest predation, total nest failure, or hatching success. Temporal variation in climate influenced percentage of total nest failure and cohort sex ratio, but not depredation rate, mean clutch size, or mean hatching success. Total hatchling recruitment in a year was influenced primarily by temporal variation in climate-independent factors, number of nests constructed, and depredation rate. Recruitment of female hatchlings was determined by stochastic variation in nest depredation and annual climate and also by the total nest production. Overall population demography depends more strongly on annual variation in climate and predation than it does on the intricacies of nest-specific biology. Finally, we demonstrate that recruitment of female hatchlings translates into recruitment of breeding females into the population, thus linking climate (and other) effects on early life stages to adult demographics.

Nest Predators of Ground-nesting Birds in Montane Forest of the Santa Catalina Mountains, Arizona

Abstract We used time-lapse video cameras and track plates to identify nest predators of Red-faced Warblers (Cardellina rubrifrons) and Yellow-eyed Juncos (Junco phaeonotus) in high-elevation (> 2,300 m) forests of the Santa Catalina Mountains in southeastern Arizona. Mammals, especially gray fox (Urocyon cinereoargenteus) and cliff chipmunk (Tamias dorsalis), were the principal nest predators of Red-faced Warblers and Yellow-eyed Juncos within our study system, accounting for 89% of all nest depredations. Our study is one of the first to use video cameras at real nests to document the prevalence of nest predators in montane forest ecosystems. Additional research is needed to learn if mammals are the dominant nest predators in other montane environments.

Spatio-Temporal Variation in Predation on Artificial Ground Nests: A 12-Year Experiment

Predation on artificial ground nests placed along four transects (alderwood, fallow, pine forest and fallow-forest edge) was studied in 1998–2009. On average, a 25.4% increase in overall predation rate was observed over the study period and increasing predation occurred at all sites. Mean multiannual predation rate differed up to 2.3-fold between transects and was highest in the alderwood and lowest in the fallow area. Despite that share of particular predators in depredation of nests was not random with respect to the studied habitats, high year-to-year variation in the pattern of predation was recorded. Between-year and between-transect changes in predation pressure were responsible for 48% of overall predation variability. Predation in one, randomly selected year was weakly related to averaged data from all 12 years, which indicates that short-term studies employing artificial nests can significantly over- or underestimate the contribution of particular species to overall predation.

Common Eider (<i>Somateria mollissima v-nigrum</i>) Nest Cover and Depredation on Central Alaskan Beaufort Sea Barrier Islands

Female common eiders (Somateria mollissima v-nigrum) generally select nest sites in areas with driftwood cover. Previous studies of common eiders have shown a positive relationship between nest success and driftwood cover. Our observations led us to hypothesize that cover does not enhance nest success when mammalian predators are present. To evaluate nest cover selection in common eiders, we examined five years of nesting data to determine the interactions between the probability of nest activity and the amount of driftwood cover in the presence of avian versus mammalian predators. Most common eider nests were surrounded by low (40%) or moderate (38%) driftwood cover. Nest failure rates were high (32%– 95%), and arctic foxes (Alopex lagopus), alone or with polar bears (Ursus maritimus), appeared to be more destructive than glaucous gulls (Larus hyperboreus) to eider nests. Logistic regression was used to model common eider nest activity associated with driftwood cover and predators. When glaucous gulls were the only predators, more driftwood cover consistently increased the probability of nest activity. But when foxes were present, nest activity consistently decreased with increasing cover. Our models support our observations that nest cover was beneficial to eiders when glaucous gulls alone were predators. Driftwood cover may be most important for the thermal and structural protection it offers, rather than for the camouflage it provides. The energetic benefit provided by driftwood windbreaks coupled with the common eider’s behavioral response of decreased nest attendance, or increased exposure to avian depredation of nests as energy reserves are depleted during incubation, provides an explanatory mechanism for our model results.

Effects of Rattus spp. Control Measures and Nesting Substrate on Nest Depredation, East Maui, Hawaii

We monitored natural and artificial nests during a two-part study on East Maui, Hawaii, designed to examine factors influencing nest depredation by black and Polynesian rats. The first half of the study examined the effects of rat control on nest depredation within portions of the Hanawi Natural Area Reserve. Rat density monitoring indicated control efforts had significantly reduced black rat captures in treatment areas, but no differences in survival of artificial or natural nests between treatment and control areas were observed. The second half of the study examined the effect of nesting substrate on nest depredation in the Makawao Forest Reserve during June 2003 and June 2004. We chose fruiting and non-fruiting nest substrates for artificial nests in two habitat types, native ohia/koa forest and an adjoining forest dominated by non-native tropical ash. Results from snap trapping showed that the relative density of black rats was significantly higher in the ohia/koa forest than the tropical ash forest, but plots with more rat captures did not always have higher rates of nest depredation as predicted. Our findings suggest that there is a large degree of variability in nest depredation by Rattus spp., but that rat density, forest type, and nest substrate influence nest depredation rates.

Biotic and Abiotic Factors Governing Nestling-period Length in the Ovenbird (Seiurus aurocapilla)

ABSTRACT. In many songbirds, the nesting period for a breeding attempt is extremely short, often lasting only a few weeks. Breeding adults can shorten this period by decreasing the number of eggs laid or reducing the length of the nestling period. Nestling-period length has received little attention in the literature but could have profound effects on annual fecundity, because each day represents a risk of nest depredation. Consequently, we were interested in assessing the biotic and abiotic factors that govern the nestling period in the Ovenbird (Seiurus aurocapilla). We provide evidence that food availability, more than predation pressure and climatic factors, influences nestling-period length, with increases in food availability decreasing the nestling period. We suggest that the nestling period is dictated by physiological constraints, which may be influenced by food availability and, thus, the ability to provision young. However, the greatest variation in nestling period was individual variation amon...

Effects of Prescribed Fire on Depredation Rates of Natural and Artificial Seaside Sparrow Nests

We compared depredation rates of natural and artificial nests of Seaside Sparrows (Ammodramus maritimus) within winter burned and unburned marsh breeding habitats. Natural nests on burned sites in 2002 were depredated at a higher rate (35.3%) during the incubation stage, compared to unburned sites (13.3%). Depredation rates of natural nests were similar between burn treatments during the nestling stage. Artificial nests exhibited significantly higher depredation rates during the incubation stage on burned compared to unburned sites in 2002. No artificial nest studies were conducted in 2003, but we examined natural nest depredation rates. Depredation rates on natural nests in 2003 were similar between burned and unburned sites during both incubation and nestling stages. Differences in nest depredation rates between 2002 and 2003 may be due to increased rainfall in 2003 leading to higher biological productivity, reduced burn effectiveness and coverage, as well as a change in nest placement by Seaside Sparrows on burned sites. Shrub-nesting species may not be as vulnerable to higher rates of nest depredation induced by prescribed burning because fire appears to only minimally impact woody shrubs, while greatly reducing biomass of herbaceous vegetation.

Spatial Ecology of Breeding Least Bitterns in Northwest Missouri

We examined the spatial ecology of breeding Least Bitterns (Ixobrychus exilis) on Squaw Creek National Wildlife Refuge in northwest Missouri using radiotelemetry. We collected 1,585 locations for 60 individuals (28 males, 32 females) during 23 May–2 August 2005 and 6 June-18 July 2006. Pooled data for both males and females, and both years resulted in mean 50 and 95% fixed kernel home range use distributions of 37.6 (n = 25) and 223.2 ha (n = 25) for all individuals with ≥30 locations. The mean maximum distance traveled between telemetry observations was 2,147.1 m (n = 28). There were no differences in home range size or mobility between male and female Least Bitterns, although there were great variations between years with birds in 2006 using home ranges five times larger than those in 2005. Habitat use was disproportionate to availability with birds using sites with cattail (Typha spp.) and arrowhead (Sagittaria spp.) to a greater extent than available in both 2005 and 2006. One of eight pairs monitored successfully reared young, while females of seven other pairs renested with new mates. Apparent nesting success was low due to severe weather events and nest depredation. We did not observe double brooding. Our study demonstrates that Least Bitterns are capable of using much larger home ranges than previously observed.

Nesting ecology and offspring recruitment in a long‐lived turtle

The role of early life stages (eggs, neonates, and juveniles) for population persistence in long‐lived organisms is thought to be minor. However, few long‐term data sets are available to test this assumption. Variation in vital rates over space and time and the potential for the success of early life stages to shape adult reproductive behavior evolutionarily suggest that more thorough consideration of these life stages is necessary. In particular, the impact of climatic variation on early life‐stage recruitment is not well understood. Furthermore, predation occupies a significant role in theoretical models of population dynamics, but its impact on populations through variable vital rates of early life stages is unknown. Maternal nest‐site choice, an important component of nesting ecology, may influence many offspring traits and respond to selection to optimize offspring success. Overall, we have limited information regarding the long‐term patterns of natural fluctuations in the nesting ecology and hatchling recruitment of populations of long‐lived organisms.The research site for this ongoing long‐term project is on an island in the Mississippi River near Thomson, Illinois, USA. Painted turtles (Chrysemys picta) have been studied extensively at this location since 1989 to examine the ecology and potential demographic consequences of nest‐site choice and depredation, with the aim of understanding the evolution of maternal nesting behavior and its effects on offspring phenotype. We monitored the site every day of the nesting season each year to record nesting and depredation events. The data presented here include nesting phenology, nest vegetation cover, total number of nesting events, clutch size, depredation, and hatchling survival.Portions of this data set have been used to address related questions in ecology and evolutionary biology. In particular, climatic variation influences the probability of nest depredation events. Such events are typically nonrandom, primarily occurring adjacent to habitat edges. Because habitat edges may have atypical vegetation composition and vegetation influences nest temperature, such nonrandom depredation could influence offspring recruitment and, hence, population structure. Given the unique scope and accessibility of this data set, researchers and teachers should find it to be a valuable empirical resource for exploring important facets of nesting ecology and hatchling recruitment in a wild population of a long‐lived species.The complete data sets corresponding to abstracts published in the Data Papers section of the journal are published electronically in Ecological Archives at 〈http://esapubs.org/archive〉. (The accession number for each Data Paper is given directly beneath the title.)

Wood Warbler Phylloscopus sibilatrix: a nomadic insectivore in search of safe breeding grounds?

Capsule Wood Warbler population crashes coincided with local rodent outbreaks; arriving birds did not settle when rodent densities were high, apparently perceiving such conditions as too dangerous. Aims To look for causes of Wood Warbler nomadic behaviour, and to check whether local fluctuations were due to variation in weather, food availability or perceived predation risk. Methods Using long‐term data from Białowieża National Park (eastern Poland) we checked whether variation in Wood Warbler numbers and nesting success were related to temperatures during spring arrival, availability of folivorous caterpillars or to rodent numbers. Results Neither Wood Warbler numbers, nor rates of their change were correlated with temperatures. Numbers of birds were positively correlated with the numbers of caterpillars, but nesting success during caterpillar outbreaks was not especially high. High rodent numbers coincided with low Wood Warbler numbers and strong numerical declines of Wood Warblers. The expectation of higher nest depredation during the outbreaks was only partially confirmed. Conclusion The results are consistent only with the safety hypothesis: the arriving Wood Warblers refused to settle in rodent outbreak areas. Thus, Wood Warbler nomadic behaviour could result from their attempts to find safe breeding places.

Red-cockaded Woodpecker (Picoides borealis) Response to Nest Depredation by an Eastern Rat Snake (Elaphe alleghaniensis)

Abstract We report the depredation of a Picoides borealis (Red-cockaded Woodpecker) nest by an Elaphe alleghaniensis (Eastern Rat Snake). Of 38 banded woodpecker groups monitored by video surveillance during 1998–2000, we documented one nest depredation by an Eastern Rat Snake. Woodpecker visitation to the nest area during the depredation event increased substantially compared with pre-depredation nesting behavior. Woodpecker visitation to the nest cavity was minimal during the first six hours after the snake was discovered by the adult woodpeckers. Visitation levels by woodpeckers remained higher than pre-depredation levels while the snake remained in the nest cavity. After the snake's departure from the nest, visitation rates dropped below pre-depredation levels. Woodpeckers continued to visit the cavity during the day and roost in the cavity at night for the remaining seven days of surveillance post-depredation. This same banded woodpecker pair nested in the same cavity in 1999 and fledged 1 female. Ov...

Environmental correlates of nesting in loggerhead turtles, Caretta caretta

Little is known about the specific environmental cues that gravid females use to initiate nesting behaviours, especially in aquatic species that are restricted to nesting in terrestrial environments. I used 15 atmospheric and oceanic environmental variables to help explain the nightly variation in the number of loggerhead turtle nests laid and the proportion of emergences that resulted in a nest. The number of nests laid was related to principal components weighted heavily by rainfall (positive association) and tidal cycles (nesting occurred when tides were moderate), although the predictive power of the environmental variables was limited. In addition, a higher proportion of emerging females laid nests during nights associated with other factors, including temperature and maximum tidal cycles. Since rainfall is commonly associated with nesting in many turtle species, I also tested the hypothesis that nesting on nights during rainfall results in a lowered probability of nest depredation. However, I found no support for this hypothesis. The turtle's large body size makes it unlikely that nesting during rainfall slows evaporative water loss or makes it easier to dig nests by softening the sand, but there may be other reasons for associating nesting with rainfall events, for example locomotion may be more efficient in moist sand. Nesting female loggerhead turtles appear to use multiple environmental cues to guide their nesting behaviours, and may use different sensory processes to determine when the weather is suitable for emerging from the ocean, and subsequently whether the conditions are conducive for laying eggs.

BREEDING ECOLOGY OF THE MANGROVE WARBLER (DENDROICA PETECHIA BRYANTI) AND COMPARATIVE LIFE HISTORY OF THE YELLOW WARBLER SUBSPECIES COMPLEX

It is widely accepted that tropical birds differ from temperate species in life-history traits and social behaviors, yet baseline ecological data are lacking for most tropical species and comparative studies often fail to control for phylogenetic influences. Within the Americas, the Yellow Warbler (Dendroica petechia) is ideal for such comparisons because its subspecies encompass a range of life-history strategies; the subspecies include long-distance migrants, temperate–tropical migrants, and tropical residents. We collected baseline data on the breeding ecology of Mangrove Warblers (D. p. bryanti) from southern Mexico (2001–2003) and compared their life-history traits with those of temperate and other tropical subspecies using existing data. Mangrove Warblers actively defended territories year-round during both nonbreeding and breeding seasons. The timing of breeding varied by year, and clutch size averaged 2.9 ± 0.5 [SD] eggs, with both a median and a mode of 3 eggs. Annual estimates of nesting success ranged from 18% to 33%, and nest depredation was the primary cause of nest failure. Annual survival was significantly higher for males (0.65) than for females (0.52) and, given our data, did not vary by age or year. On the basis of a comparative analysis of life-history data from published studies on the Yellow Warbler subspecies complex, we found that most life-history traits differed between tropical and temperate latitudes. Specifically, compared with temperate Yellow Warblers, Mangrove Warblers exhibited longer breeding seasons, smaller clutch sizes, longer incubation and nestling periods, lower nesting success, higher rates of nest depredation, and higher annual adult survival rates.

Breeding performance of the Fieldfare Turdus pilaris in the subalpine birch zone in southern Lapland: a 20 year study

A Fieldfare population, on average c. 160 pairs, was studied in subalpine birch forest in southern Lapland (c. 66°N; 500–600 m.a.s.l.) in 1983–2002. Onset of egg-laying showed no temporal trend, consistent with absence of spring temperature trend. Eggs were laid with an interval of c. 21 hours and 45 minutes, not 24 hours as normal in passerines. This reduces the exposure time to depredation during egg-laying with 9%. Egg hatchability was 96%. Egg parasitism never occurred. Depredation of nests was 46%, but very variable. Replacement and second clutches did not occur. Although an average of 4.45 young fledged from successful nests (≥1 fledgling), only 2.11 fledglings were produced per pair and year. The population varied without trend over the study period. Adult survival, estimated by the proportion of adults at the start of breeding, was 58%. This infers that first year survival must be at least c. 40%. Since this is a likely value, it seems that the Fieldfare population of the subalpine birch forest is selfsustained and not dependent upon immigration.

Division of labour during incubation in a woodpeckerColaptes auratuswith reversed sex roles and facultative polyandry

The contribution of males to incubation has rarely been studied in altricial birds because the pursuit of extra mating opportunities is believed to conflict with incubation. Woodpeckers show reversed sex roles in parental care with males doing most of the nest construction, incubating and brooding of the young while females may be polyandrous. I investigated incubation by each sex at 71 monogamous and four polyandrous nests of the Northern FlickerColaptes auratus, predicting that males would contribute to incubation according to their energy reserves (body condition) whereas females would contribute based on alternate reproductive opportunities. Nest attendance was 99% with males contributing a mean of 66% of the total incubation including nocturnal incubation. The length of daytime bouts averaged about 2 h and did not differ between the sexes. Consistent with predictions of investment strategies, structurally larger males and those in poorer body condition incubated less than smaller males, perhaps because they required more recess time to forage or to conserve energy. Older females contributed less incubation than young females and polyandrous females contributed less incubation at their secondary nests than monogamous females. Incubation period, nest depredation rate and hatching success were not influenced by bout length, number of bouts or relative contribution of the sexes. Hatching success was 86% at nests of both monogamous and polyandrous females because males compensated for reduced female participation. Because incubation of the sexes is compensatory and not additive, incubation pattern did not influence short‐term reproductive success. I conclude that males invest in incubation according to their energy needs, and females may adjust their contributions based on alternate reproductive tactics.

Utilizing material from old nests - a way to time-saving in a short breeding species? The case of the Long-tailed Tit Aegithalos caudatus

The Long-tailed Tit (Aegithalos caudatus) is a species characterized by high levels of nest depredation and a short breedingseason. In the face of such high levels of nesting failures, behavioural adaptations to reduce failures should be expected.Here I report on two cases where Long-tailed Tits appeared to reduce their re-nesting interval by utilizing material fromdestroyed nests to build new ones. I suggest that using a previous nest to build a subsequent nest is an adaptation in Longtailed Tits aimed at increasing the speed with which a pair can begin to re-nest and hence increasing their breeding success in a given year.

Marking Nests Increases the Frequency of Nest Depredation in a Northern Population of Painted Turtles (Chrysemys Picta)

Predators use visual and olfactory cues to locate turtle nests. Since 1999, we marked Painted Turtle (Chrysemys picta) nests at a long-term study site by inserting Popsicle™ sticks part way into the nest cavity. Because nest-marking provides a cue to potential predators, we tested whether nest-marking increases nest depredation rates. During the nesting season, 15 artificial nest pairs (N = 30 artificial nests in total) were created by digging and refilling holes (presumably emulating nest excavation by turtles) at a nesting site. Nests in each pair were 45 cm apart, but only one nest in each pair was marked with a Popsicle™ stick, and no eggs were placed in either hole. After one week, depredation was observed in nine of the 15 nest pairs, and all depredation events were directed towards marked nests. A Binomial Test revealed that this pattern was significantly nonrandom. It is possible that predators were responding to olfactory cues left by Popsicle™ sticks, and given that mammalian predators are common at our study site, we cannot rule out the possibility that such olfactory-oriented predators depredated artificial nests. However, we suspect that Common Ravens (Corvus corax) and American Crows (Corvus brachyrhynchos; nest predators that are visually oriented) were the primary predators in this study. Future experiments should use turtle eggs in both marked and unmarked nests to evaluate whether the markers represent a significant mortality factor for Painted Turtle eggs.

Breeding behaviour and ecology of the grey fantail (Rhipidura albiscapa)

The grey fantail (Rhipidura albiscapa) is a common Australian flycatcher, yet no detailed reports have been made of its breeding ecology. A population of grey fantails was studied over four seasons in the Australian Capital Territory. Males had large testes and pronounced cloacal protuberances, morphology suggestive of sperm competition. Although two polyandrous trios were observed, most individuals bred as part of a season-long monogamous pair, suggesting that extra-pair copulation may be the principal cause of sperm competition. Indeed, behavioural observations revealed that males regularly intruded other territories, targeting those with building, rather than incubating, females. Intruding males were observed harassing, attempting to copulate and successfully copulating with resident females. Males did not mate guard, but regularly attacked their mates during each building attempt. Despite the probability that extra-pair paternity is common in this species, grey fantails were monomorphic and monochromatic, with a high level of paternal care. Nest depredation was common, with 83% of all clutches depredated before fledging. High levels of male care in care in this species may be better explained by an increase in fledging success associated with high male contribution to offspring care than confidence of paternity.