Predator–prey interactions between the South Polar skua Catharacta maccormicki and Antarctic tern Sterna vittata

Antarctic terns have to co‐exist in a limited space with their major nest predator, the skuas. We conducted artificial nest experiments to evaluate the roles of parental activity, nest location and nest and egg crypsis in this simple predator–prey system. Predation on artificial (inactive) nests was higher in traditional nesting sites than in sites previously not occupied by terns, which suggests that skuas memorized past tern breeding sites. Predation on artificial nests in inactive colonies was higher than in active (defended) colonies. Parental defense reduced predation in colonies to the level observed in artificial nests placed away from colonies. This suggests that communal defense can balance the costs of attracting predators to active colonies. Within colonies, predation was marginally higher on experimental eggs put in real nests than on bare ground. Although it seems that the presence of a nest is costly in terms of increased predation, reductions in nest size might be constrained by the need for protective nest structures and/or balanced by opposing selection on nest size. Predation did not differ markedly between artificial (quail) and real tern eggs. A simultaneous prey choice experiment showed that the observed predation rates reflected egg/nest detectability, rather than discrimination of egg types. In summary, nesting terns probably cannot avoid being detected, and they cannot defend their nest by attending them. Yet, by temporarily leaving the nest, they can defend it through communal predator mobbing, and at the same time, they can benefit from crypsis of unattended nest and eggs.     

Timing of Spawning and Host-nest Choice for Brood Parasitism by the Japanese Minnow,Pungtungia herzi,on the Japanese Aucha Perch,Siniperca kawamebari

A field study of the breeding ecology of the Japanese aucha perch, Siniperca kawamebari, and brood parasitism by the Japanese minnow, Pungtungia herzi, on nests of the perch was carried out from 1989 to 1991. Observations of perch nests under natural conditions in 1990 showed that brood parasitism by the minnow was concentrated on host nests in which nest owners had just begun their nesting cycle. When spawned in a perch nest with recently spawned perch eggs, parasite eggs always hatched earlier than host eggs. An experiment with imitation perch eggs in 1991 confirmed that changing colour of host eggs was the cue for the parasites to distinguish between different developmental stages of host eggs. Parasite eggs rapidly disappeared without guarding by a host male (Baba et al. 1990). This loss was caused by predation by fishes. Parasite fry left the nest immediately after hatching, so parasite eggs spawned in a host nest in an early stage should be well guarded until they hatch. In the field, minnows deposited their eggs in perch nests which had larger numbers of newly spawned perch eggs. Since the perch males always deserted their nests when their own eggs disappeared, the parasite's choice of host nests with larger numbers of host eggs may ensure survival of the parasite eggs. The timing of egg deposition and choice of host nest by the minnow appear to be adaptive in terms of brood parasitism on nests of the perch.     

Egg survival is related to the colour matching of eggs to nest background in Black-tailed Gulls

A long-standing hypothesis posits that, for species with exposed nests, a close match between the colour of the eggs and that of the nest in which they are laid should enhance egg survival, but this has rarely been tested in a rigorous manner. Here, we demonstrate the effects of egg–nest colour matching on egg survival in Black-tailed Gulls (Larus crassirostris) on Hongdo Island, Korea. We quantified the ground colour of eggshells and that of the nest background using a digital camera and computerized RGB and greyscale colour systems. We show that a close match of eggshell ground colour and nest background colour was associated with increased chances of eggs surviving through to hatching. In particular, there were strong survival advantages for eggs matching the nest colour in sites with poor concealment, whereas there was no effect of eggshell ground colour in nests that were more concealed by vegetation. Our findings support the hypothesis that egg colour functions to make eggs cryptic and that egg colouration may be a significant factor affecting egg loss.     

Nesting ecology of a naturalized population of Mallards Anas platyrhynchos in New Zealand

Investigating the reproductive ecology of naturalized species provides insights into the role of the source population's characteristics vs. post‐release adaptation that influence the success of introduction programmes. Introduced and naturalized Mallards Anas platyrhynchos are widely established in New Zealand (NZ), but little is known regarding their reproductive ecology. We evaluated the nesting ecology of female Mallards at two study sites in NZ (Southland and Waikato) in 2014–15. We radiotagged 241 pre‐breeding females with abdominal‐implant transmitters and measured breeding incidence, nesting chronology and re‐nesting propensity. We monitored 271 nests to evaluate nest survival, clutch and egg size, egg hatchability and partial clutch depredation. Breeding incidence averaged (mean ± se) 0.91 ± 0.03, clutch size averaged 9.9 ± 0.1 eggs, 94 ± 2% of eggs hatched in successful nests, partial depredation affected 6 ± 1% of eggs in clutches that were not fully destroyed by predators, and re‐nesting propensity following failure of nests or broods was 0.50 ± 0.003. Nesting season (first nest initiated to last nest hatched) lasted 4.5 months and mean initiation date of first detected nest attempts was 28 August ± 3.3 days. Smaller females were less likely to nest, but older, larger or better condition females nested earlier, re‐nested more often and laid larger clutches than did younger, smaller or poorer condition females. Younger females in Southland had higher nest survival; cumulative nest survival ranged from 0.25 ± 0.007 for adult females in Waikato to 0.50 ± 0.007 for yearling females in Southland. Compared with Mallards in their native range, the nesting season in NZ was longer, clutches and eggs were larger, and nest survival was generally greater. Different predators and climate, introgression with native heterospecifics and/or the sedentary nature of Mallards in NZ may have contributed to these differences.     

Effects of nest-site characteristics and parental activity on cowbird parasitism and nest predation in Brown-and-yellow Marshbirds

ABSTRACT Nest‐site selection and nest defense are strategies for reducing the costs of brood parasitism and nest predation, two selective forces that can influence avian nesting success and fitness. During 2001–2002, we analyzed the effect of nest‐site characteristics, nesting pattern, and parental activity on nest predation and brood parasitism by cowbirds (Molothrus spp.) in a population of Brown‐and‐yellow Marshbirds (Pseudoleistes virescens) in the Buenos Aires province, Argentina. We examined the possible effects of nest detectability, nest accessibility, and nest defense on rates of parasitism and nest predation. We also compared rates of parasitism and nest predation and nest survival time of marshbird nests during the egg stage (active nests) with those of the same nests artificially baited with passerine eggs after young fledged or nests failed (experimental nests). Most nests (45 of 48, or 94%) found during the building or laying stages were parasitized, and 79% suffered at least one egg‐predation event. Cowbirds were responsible for most egg predation, with 82 of 107 (77%) egg‐predation events corresponding to eggs punctured by cowbirds. Nests built in thistles had higher rates of parasitism and egg predation than nests in other plant, probably because cowbirds were most active in the area where thistles were almost the only available nesting substrate. Parasitism rates also tended to increase as the distance to conspecific nests increased, possibly due to cooperative mobbing and parental defense by marshbirds. The proportion of nests discovered by cowbirds was higher for active (95%) than for experimental (29%) nests, suggesting that cowbirds used host parental activity to locate nests. Despite active nest defense, parental activity did not affect either predation rates or nest‐survival time. Thus, although nest defense by Brown‐and‐yellow Marshbirds appears to be based on cooperative group defense, such behavior did not reduce the impact of brood parasites and predators.     

Trade-offs in nest site selection in coastal populations of Lapwings Vanellus vanellus

In coastal populations of Lapwings Vanellus vanellus in southwestern Sweden, arable fields predominated as foraging habitat before laying. Females caught more large prey items on arable fields and shores than on pastures. Close to egg laying, females foraged mainly near their future nest sites. Arable land and pastures were used to a similar extent for nesting. We found no difference in nest predation between habitats. Egg volume varied among females and was correlated with wing-length, body mass and condition. Mean egg volume also was positively correlated with feeding time on arable land before laying. Pairs nesting on arable fields therefore generally produced larger eggs than those on pastures. The distances between nests and chick foraging areas, however, were significantly longer for birds nesting on arable land than for those on pastures. Moreover, in 2 of 3 years, the proportion of hatched chicks that survived until fledging was negatively correlated with this distance. There was no difference in chick survival between broods hatched on arable fields and pastures. We suggest that nest site selection and offspring production involve a trade-off between the benefits of nesting close to rich feeding grounds for adults and the costs of moving long distances between nest sites and chick-rearing areas.     

Sea Turtle Nesting as a Process Influencing a Sandy Beach Ecosystem

Sea turtle egg mortality, egg predation, and small organisms associated with turtle nests were studied at Playa Ostional, Costa Rica. Sites with concentrated sea turtle nesting were compared with solitary nesting sites as a function of place and time based on ANOVA, Akaike's Information Criterion, and Bayesian analyses. Results indicate that sea turtle egg mortality was significantly associated (P < 0.005) with flowing water that erodes or saturates nesting sites, and with overlapped nesting in which sea turtles disturb each other's nests. Sarcophagid and calliphorid fly larvae (Bayesian prior = 1.19; posterior = 2.27), fungi (prior = 1.14; posterior = 1.92), mites (prior = 0.51; posterior = 1.15), and several other types of small organisms increased in number after turtle egg laying (N= 303 nests; 34,451 turtle eggs). During peak sea turtle nesting periods, visitation to nesting sites by poachers and vertebrate predators was high, and relative number of nests disturbed by these predators was low (P < 0.02). In multimodel analysis, the three most parsimonious models were: (1) turtle egg mortality and distance from mean high tide; (2) turtle egg predation and distance from mean high tide; and (3) turtle egg mortality and nesting density, with Akaike weights of 0.224, 0.203, and 0.153 respectively. Intensive sea turtle nesting might result in upwelling and turnover of nesting debris and nest organisms, and may influence biotic community structure of sandy beach ecosystems.     

Predation of Lapwing Vanellus vanellus nests on lowland wet grassland in England and Wales: effects of nest density, habitat and predator abundance

There is concern that predation of Lapwing Vanellus vanellus nests may create additional pressure on declining populations of this species in Europe. At seven sites in England and Wales, daily nest predation rates on 1,390 nests were related to variables using Generalised Linear Mixed Models. The strongest predictor was Lapwing nest density (number of nests within 100 m): predation rates declined as nest density increased. Since nocturnal species, probably mammals, have been identified as the major predators of Lapwing nests at these sites, these results suggest that Lapwings are able to deter mammalian predators or may settle to nest at high densities in areas with low predation pressure. At the site level, there was no relationship between Lapwing nesting density and fox density, and a positive relationship with Carrion Crow Corvus corone nesting density. There was a weaker effect of distance to field boundary: nests closer to boundaries were more likely to be predated. Weak interactive effects between crow density and both nest visibility and distance to vantage point were identified in models using a reduced subset of nests. These were counter-intuitive, did not persist in the larger data set, and do not have obvious explanations. If Lapwings nesting at high density are able to deter predators, there are implications for land management. Smaller areas could be managed within potential breeding habitat to encourage Lapwings to nest in dense colonies. Selection of larger fields for such management, where nests could be located far from the field boundary should improve the value of such measures.     

Breeding biology of Eared Quetzals in the Sierra Madre Occidental, Mexico

ABSTRACT.   Eared Quetzals ( Euptilotis neoxenus ), a threatened species, are one of the least studied trogons in Mexico. We monitored 29 Eared Quetzal nests in the Chihuahuan portion of the Sierra Madre Occidental from 1998 to 2003. All nests were in tree cavities, and the mean tree and nest cavity heights ( N = 14) were 16.9 ± 7.8 m and 11.4 ± 4.1 m, respectively. The mean clutch size was 2.8 ± 0.9 eggs ( N = 28), the incubation period lasted 22 d ( N = 1), and nestling periods ranged from 29 to 31 d ( N = 5). Both adults incubated eggs and fed nestlings. Of 80 eggs, 70 hatched (87.5%) and 67 of 70 young fledged (95.7%). Twenty-five of 29 nests (86.2%) produced at least one fledgling. One nest was predated, and two failed when nest trees fell. Higher rates of nest predation have been reported for other species of trogons. However, fewer potential predators, such as snakes and mammals, are present in the Sierra Madre than in tropical zones where most trogon species occur. In addition, antipredator behaviors, including nestlings with calls resembling a snake and nests with an unpleasant odor, may contribute to the high nesting success. The main limiting factors for Eared Quetzals in the northern Chihuahua may be competition for cavities with other secondary cavity-nesters, and the failure of nests when snags fall.     

Differential predation by mammals and birds: implications for egg-colour polymorphism in a nomadic breeding seabird

Selection for crypsis in varying environments has long been established as the main evolutionary force promoting the huge variation in avian egg coloration. In several avian species, variation in egg coloration exists, but available information available on the relative success of these different colour morphs against predation is scarce. We investigated the value of eggshell coloration against mammal and avian predators in the South American Tern, Sterna hirundinacea. We found evidence of a relationship between particular eggshell ground coloration and success against predation, in different tern colonies, where strong selection was caused by single avian and mammalian predator species. Survival to hatching of eggs with greenish ground coloration was greater than in eggs of the remaining colours when a mammalian carnivore was present. This implies that the human visual system does not accurately represent predator perception but that, viewed through the predator's eyes, the conspicuous greenish eggs are well concealed. The rate of artificial nest predation by visually searching gulls was higher for eggs more conspicuous to the human eye than for eggs more closely resembling the nest substrate. The evolution of polymorphisms in eggshell ground colour may have resulted from differences in the type of predator present, and differences in choice of breeding site varying in the background substrate. The nomadic breeding behaviour of terns may imply that females differing in the frequency of alleles expressing particular egg coloration, selected for in particular environments, may eventually gather in some colonies, thus producing the observed intracolony variation in egg coloration. We hypothesise that egg colour variation could be maintained in the population by shifting peaks of predation impact in the different locations where colonies form, e.g. islands without mammalian predators vs. mainland sites.     

Factors affecting piping plover hatching success on Long Island,New York

Low hatching success may limit progress towards reaching productivity goals for Atlantic Coast piping plover (Charadrius melodus) recovery, despite management strategies to protect eggs from predators and decrease human disturbance of birds on nests. We measured piping plover hatching success on Eastern Long Island beaches and identified the major causes of egg failure to better understand why eggs that were otherwise intact (not depredated or destroyed by tidal flooding) failed to hatch. We documented egg and nest fates, dissected contents of unhatched eggs to determine viability, and recorded human and predator activity near a subset of plover nests on Suffolk County Parks properties. The low hatching success we recorded (0.60) in 2006 and 2007 would require higher chick survival rates than are typically observed for piping plovers to meet recovery targets for productivity. Few eggs showed signs of poor viability and overall egg hatchability was comparable to other ground nesting birds. Most egg failure was due to either depredation at unexclosed nests or nest abandonment by adults. The best predictor of nest abandonment was the maximum number of red fox tracks (Vulpes vulpes) counted on nearby transects (β = −1.16, 95% CI: −2.0 to −0.3) and we found evidence that plovers abandoned eggs in response to predation risk (e.g., a fox circling a nest exclosure). Adults from abandoned nests may have deserted eggs or been depredated. In either case, intact and viable eggs were abandoned. Nest abandonment was not related to human activity near nests, which were buffered from human disturbance by symbolic string fencing. Our results suggest that depredation and nest abandonment (e.g., desertion or death of adults) due to predator disturbance, not human disturbance or poor egg viability, contributed to the low hatching success we recorded. Active predator removal in addition to modification of predator exclosure use and design may be necessary to prevent direct (egg depredation) and indirect (nest abandonment) negative effects of predators on hatching success. © 2010 The Wildlife Society.     

Avian eggshell thickness in relation to egg morphometrics,embryonic development,and mercury contamination

Eggshell thickness is important for physiological, ecological, and ecotoxicological studies on birds; however, empirical eggshell thickness measurements for many species and regions are limited. We measured eggshell thickness at the equator and the egg poles for 12 avian species and related eggshell thickness to egg morphometrics, embryonic development, egg status, and mercury contamination. Within an egg, eggshells were approximately 5.1% thicker at the equator than the sharp pole of the egg, although this difference varied among species (0.6%–9.8%). Within Forster's tern (Sterna forsteri), where eggshell thickness was measured at 5 equally spaced positions along the longitude of the egg, eggshell thickness changed more rapidly near the sharp pole of the egg compared to near the blunt pole of the egg. Within species, eggshell thickness was related to egg width and egg volume for six of the 12 species but was not related to egg length for any species. Among species, mean eggshell thickness was strongly related to species mean egg width, egg length, egg volume, and bird body mass, although species mean body mass was the strongest predictor of species mean eggshell thickness. Using three species (American avocet [Recurvirostra americana], black‐necked stilt [Himantopus mexicanus], and Forster's tern), whose nests were carefully monitored, eggshell thickness (including the eggshell membrane) did not differ among viable, naturally abandoned, dead, or failed‐to‐hatch eggs; was not related to total mercury concentrations of the egg content; and did not decrease with embryonic age. Our study also provides a review of all existing eggshell thickness data for these 12 species.     

Snowy plover nest site selection,spatial patterning,and temperatures in the Southern High Plains of Texas

Snowy plover (Charadrius nivosus) populations have declined throughout their range, in part because of habitat degradation and poor nest success, making information regarding regionally specific nest site selection and spatial patterns important when considering habitat conservation and management guidelines. We determined nest site selection characteristics (n = 180) and examined spatial patterns (n = 215) of snowy plover nests in saline lakes in the Southern High Plains (SHP) of Texas. At 104 nests, we examined the influence of substrate type on nest temperatures and heat mitigation. Snowy plover nests were more likely to be found near an object, on pebble substrate, and with fewer plants than random sites. High use areas were generally located in areas with pebble substrate and on human-made or natural islands, berms, and peninsulas. Overall, nests placed on pebble substrate had lower temperatures during the day than nests placed on sand substrates. Nest placement on pebble substrate may be valuable to nesting snowy plovers, providing thermal advantages to incubating adults and depressing potentially high nest predation rates. Management guidelines for this region should emphasize the importance of addressing key elements of snowy plover nesting habitat including the presence of pebble substrate and reducing vegetation encroachment. © 2012 The Wildlife Society.     

Communal egg-laying behaviour and the consequences of egg aggregation in the brown anole (Anolis sagrei)

Communal nesting is a behaviour that involves multiple females laying eggs in the same nest or nesting site. This behaviour may be a consequence of a shortage of preferable nest sites (constraint hypothesis) or an adaptation generated by fitness benefits associated with egg aggregation (adaptive hypothesis). Experimental tests of these hypotheses require information about maternal nest site choice and its fitness consequences. To address these, we studied a lizard (brown anole; Anolis sagrei) that produces single-egg clutches, but often aggregates eggs in nest sites. In a lab study, females were given the option of nesting in (a) soil previously used as nest substrate vs. fresh soil and (b) soil with eggshells vs. without eggshells. We also experimentally examined the effects of egg aggregation by incubating eggs singly, in groups of four, and in groups of nine. We recorded egg surface temperature, water uptake, and hatchling morphology. Females were more likely to nest in pots with used soil and with eggshells than in pots with fresh soil or without eggshells. We observed no effects of egg aggregation on egg survival, egg temperature, or most measures of hatchling morphology. However, singly-incubated eggs absorbed more water than eggs incubated in the four and nine egg aggregations and this resulted in offspring with greater body condition (i.e. heavier for their length) at hatching. The behavioural experiment demonstrates that females actively choose nest sites that have been used previously (as expected under the adaptive hypothesis), but the egg-aggregation experiment shows no benefits to offspring based on the variables measured. Thus, results of the behaviour study support the adaptive hypothesis; however, results from our egg-incubation study do not. Likely, the adaptive and constraint hypotheses are not mutually exclusive, and a diversity of factors influence the evolution of communal nesting behaviour.     

Different nest predator guild associated with egg size in the Patagonian temperate forest

Capsule: Studies of nest predation using artificial nests need to consider the effect of egg size on the types of predator that are detected.

Aims: To estimate the nest predation rate in the Patagonian temperate forest and evaluate the influence of egg size on predator guild.

Methods: On different plant species, we placed 108 nests each containing eggs of either Atlantic Canary Serinus canaria or Common Quail Coturnix coturnix, and a model clay egg of equal size to the real egg. Nest predators were identified from the marks left on the clay eggs or by videos recorded using camera traps.

Results: 86% of the nests were predated. Birds, mainly Chimango Caracara Milvago chimango, were the main nest predators. A marsupial, the Monito del Monte Dromiciops gliroides, and rodents also contributed to nest predation. Nest predation rates were similar for both egg sizes but the nest predator guild was different. Birds and rodents preyed on both eggs but the Monito del Monte consumed mainly small eggs.

Conclusion: Egg size did not influence the rate of nest predation but, instead, affected the nest predator guild. Consequently, in order to avoid underestimating the impacts of small predators, egg size should be considered in studies of nest predation.     

Variation in male‐built nest volume with nesting‐support quality,colony, and egg production in whiskered terns

Nest building can represent an energetically costly activity for a variety of animal taxa. Besides, the determinants of within‐species variation in the design of nests, notably with respect to natural and sexual selection, are still insufficiently documented. Based on an observational study, we examined the influence of nesting conditions (nesting‐support quality, colony, laying date, and year) on male‐built nest volume and also its potential role as a postmating sexually selected display in the whiskered tern Chlidonias hybrida. This tern species is a monogamous colonial bird with obligate biparental care breeding on aquatic vegetation. Hence, large nesting platforms are expected to be a selective advantage because they would better withstand adverse environmental conditions and provide a secure structure for eggs. Nest size may also serve as a postmating sexual trait, and variation in egg production would be positively associated with nest size. We found that nest volume was adjusted to different environmental cues. A positive relationship was found between nest volume and nesting‐support quality, indicating that the leaf density of white waterlily is essential for nest stability. Variation in nest volume was not correlated to colony size but varied among colonies and years. Male‐built nest volume was also positively associated with mean egg volume per clutch but not with clutch size. The fitness consequences of building a large nest are yet to be studied, and additional investigations are recommended to better understand whether the activity of males early during breeding season (e.g., nest building and courtship feeding performance) really serves as postmating sexually selected signals.     

Nesting in a thermally challenging environment: nest‐site selection in a rock‐dwelling gecko,Oedura lesueurii (Reptilia: Gekkonidae)

In egg‐laying species, maternal oviposition choice can influence egg survival and offspring phenotypes. According to the maternal‐preference offspring‐performance hypothesis, females should choose oviposition sites that are optimal for offspring fitness. However, in thermally challenging environments, maternal oviposition behaviour may be constrained by the limited availability of suitable oviposition sites. We investigated nest‐site selection in a nocturnal lizard [velvet gecko Oedura lesueurii (Duméril and Bibron)] that inhabits a thermally challenging environment in south‐eastern Australia. The viability of these gecko populations is critical for the persistence of an endangered snake species (Hoplocephalus bungaroides Wagler) that feeds heavily on velvet geckos. Female geckos chose nest sites nonrandomly, with 87% of nests (N = 30) being laid in deep crevices. By contrast, only 13% of clutches were laid under rocks, which were the most readily available potential nest sites. Nest success in crevices was high (100%), but no eggs hatched from nests under rocks. Temperatures in nest crevices remained relatively low and constant throughout the incubation period (mean = 22.7 °C, range 21.0–24.5 °C), whereas thermal regimes under rocks showed large diurnal fluctuations. Geckos selected crevices that were deeper, had less canopy cover, and were warmer than most available crevices; in 85% of cases, such crevices were used simultaneously by more than one female. The thermally distinctive attributes of nest sites, and their frequent communal use, suggest that nest sites are a scarce resource for female velvet geckos, and that the shading of rock outcrops through vegetation encroachment may influence nest success in this species. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 250–259.     

Mating system and spawning cycle in the blenny,Istiblennius enosimae,at Kagoshima,Japan

Synopsis Field observations on reproductive ecology and territoriality of the blennyIstiblennius enosimae, were made in a tidepool at Hanaze Beach, Kagoshima Prefecture, Japan during the summer of 1988. This blenny was herbivorous, and nesting males (> 73 mm SL) maintained territories around nest sites, which were located in rocky crevices of the tidepool. Males courted females wandering near their nests, and spawnings coincided with neap tides. Males guarded the eggs until the embryos hatched at following spring tides. It was suggested that this semilunar spawning cycle guarantees a maximum dispersal of newly hatched embryos away from natal tidepool. Male reproductive success was related to large body size and/or large nest size. There is a size-assortative relationship between male and female among pairs. Egg predation rates by fishes, crabs and sea urchins were not correlated with the body size of male blennies.     

Social and Thermal Cues Influence Nest‐site Selection in a Nocturnal Gecko,Oedura lesueurii

In oviparous species lacking parental care, successful reproduction depends on females selecting nest sites that facilitate embryonic development. Such sites may be limited in the environment, which can lead to multiple females using the same nest site simultaneously. However, there are several alternative explanations for communal nesting, including natal homing, predator satiation, and adaptive benefits to offspring. We used laboratory experiments to evaluate three hypotheses about nest‐site selection in velvet geckos (Oedura lesueurii), which often nest communally. We investigated whether the trend to nest communally is influenced by the following: (1) evidence of previous nesting (hatched eggshells); (2) body size; and/or (3) thermal regimes. When given the choice, females laid their eggs in shelters containing hatched eggshells rather than in empty shelters, and this was not influenced by body size. Females selected nest sites that were cooler than their own mean selected body temperatures, suggesting that thermal requirements of their developing embryos could outweigh their own thermoregulatory preferences. Field observations of natal homing and high predation rates on gravid females suggest that imprinting on nest sites and/or predator swamping also play roles in communal nesting. Collectively, our results suggest that female velvet geckos use multiple cues to select appropriate nest sites, and hence that multiple mechanisms result in communal nesting behavior in this species.     

Embryonic vocalizations mediate parental care in Masked Lapwings (Vanellus miles) but not Red-capped Plovers (Charadrius ruficapillus)

Embryonic vocalizations in birds may enable communication between embryos and incubating parents but responses of parents to embryonic vocalizations have not been measured experimentally. In two ground-nesting shorebirds, we compare parental care of eggs without embryonic vocalizations, those with natural embryonic vocalizations, and those in which we experimentally introduced embryonic vocalizations, while accounting for prevailing temperatures. We continuously recorded nests (one block of up to 24 h per nest) of two ground-nesting shorebirds, the Red-capped Plover Charadrius ruficapillus and Masked Lapwing Vanellus miles and quantified parental behaviours. We predict an increase in egg thermoregulation behaviours (time spent incubating or shading) and ‘fussing’ (a combination of rising and re-settling, shuffling, orientation change and egg turning) when vocalizations were naturally present or when they were experimentally introduced in comparison to when no vocalizations were present (control). In Lapwings, the rate of fussing increased at the nest only when natural vocalizations were present; however, preening increased when natural or introduced vocalizations were present. Additionally, the frequency of bill to egg touches (inspections) increased only in the presence of introduced vocalizations. For Plovers, treatment had no influence on parental behavioural; however, the frequency of fussing, bill to egg touches and shell tossing increased with air temperature. For both species, there was no influence of the presence of the embryo’s vocalizations (natural or introduced) on the parent’s egg thermoregulation behaviours. Our results highlight that acoustic communication across the eggshell may occur and can influence parental care in shorebirds, but this appears to be species-specific.