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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. We measured eggshell thickness at the egg equator and the egg poles for 12 avian species, and related eggshell thickness to egg morphometrics, embryonic development, egg status, and mercury contamination. Our study also provides a review of all existing eggshell thickness data for these 12 species.

Egg size is a useful metric for maternal investment, offspring quality, and contaminant studies. Yet these values and the egg shape coefficients required to estimate egg size are not available for many species, including White-faced-Ibis (Plegadis chihi). We provide egg morphometrics derived from 319 White-faced Ibis eggs sampled at Bear River Migratory Bird Refuge, Great Salt Lake, Utah, from 2010 to 2012. Measured egg length (mean ± SD) was 51.20 ± 1.99 mm, egg width was 36.08 ± 1.15 mm, and whole egg mass was 34.1 ± 3.3 g. Estimated whole egg volume was 34.63 ± 3.73 cm3 and estimated egg shape coefficients were 0.507 for Kv (whole egg and egg contents), 0.547 for Kw (whole egg), and 0.524 for Kw (egg contents only). In addition, we documented expected declines in egg mass over time due to incubation (–0.22 g/d) and desiccation during storage (–0.03 g/d), that should be accounted for prior to analyses that use egg mass of freshly laid eggs.

The painted turtle (Chrysemys picta) is widely distributed from coast to coast in North America with each of four subspecies generally occupying different regions. In the southwestern USA and northern Mexico, where C. p. bellii is the expected native race, populations are small and widelyscattered. Introduced populations of other painted turtle subspecies are reported from various locations in the USA. We discovered a small but dense introduced population of C. p. marginata on the Colorado Plateau in northern Arizona, a region with few, if any, turtles due to aridity and an elevated topography with little surface water. The turtles were in a remote pond constructed to provide cattle with water. Chrysemys p. marginata occur naturally east of the Mississippi River, over 2,000 km away. The nearest native population of C. p. bellii in Arizona is over 160 km away. We observed nesting females, juveniles, and the presence of shelled eggs in females via Xradiography confirming a self-sustaining population. The body sizes and nesting season we observed were consistent with data for those variables from native populations of the taxon. It is unknown exactly how the turtles came to be established in such a remote location, but it is unlikely that they will spread due to the scarcity of perennial water sources in the semi-arid region. Due to increasing drought frequency and duration in the region, small populations like this one, introduced into a novel environment, may be bellwethers for monitoring the effects of climate change.

Study of Great Egret breeding success was carried out for the first time in Hara Biosphere Reserve of Iran. Since Great Egret is considered as wading bird as well as wetland-dependent species which is located on top of the food chain in this ecosystem, its breeding study is an appropriate means for evaluating food supply fluctuations and environmental threatening factors by comparison of different years. On the other hand, Great Egret is considered a suitable indicator to examination of biological changes, impact of pollutions, and other effective human activities on Hara Biosphere Reserve. Therefore, read-ahead is required for area management planning in order to maintain the health of mangrove ecosystem and control threatening factors of the sensitive biodiversity of area. The results indicate that the average breeding success of Great Egret in different stages of hatching success, fledging success, and breeding success were equal to 0.54, 0.61, and 0.50 in 2008 and 0.61, 0.59, and 0.42 in 2009, respectively.

Relationships between egg volume and an array of life-history traits have been identified for many bird species. Despite the importance of egg volume and the need for precise and accurate measurements, egg volume is usually estimated using a mathematical model that incorporates length and width measurements along with a shape variable. We developed an instrument that provides precise estimates of egg volume and can be easily used in the field. Using Clapper Rail (Rallus longirostris) eggs, we compared egg volumes measured using our instrument with estimates based on linear measurements. We found our instrument to be both precise and accurate. Compared with a method based on linear measurements of eggs, use of our instrument reduced variation in egg volume estimates by 1.6 cm3, approximately 8% of the volume of a Clapper Rail's egg. Further advantages of our technique include ease of use, increased accuracy of field-based volume estimates, and increased resolution of variation in egg volume estimates. In addition, our technique does not require postdata collection processing time and did not influence hatching success. Also, for Clapper Rails and similar species, our technique can be combined with other techniques (e.g., egg flotation) so that both egg volume and embryonic stage can be estimated at the same time. /// Las relaciones entre el volumen del huevo y una gran cantidad de caracteres en las historias de vida han sido identificadas para muchas especies de aves. A pesar de la importancia del volumen del huevo y la necesidad de medidas más precisas, el volumen del huevo es comúnmente estimado usando modelos matemáticos que incorporan medidas del largo, ancho y forma del huevo. Nosotros creamos un instrumento que proporciona estimativos precisos del volumen del huevo y puede ser fácilmente usando en el campo. Usando huevos de Rallus longirostris comparamos las medidas de los volúmenes de los huevos usando nuestro instrumento con estimados obtenidos mediante mediadas lineales. Encontramos que nuestro instrumento fue preciso. Comparado con métodos que se basan en medidas lincales de los huevos, el uso de nuestro instrumento reduce la variación de los estimativos del volumen de los huevos en 1.6 cm3, aproximadamente 8% del volumen de los huevos de Rallus longirostris. Ventajas adicionales de nuestra técnica incluye facilidades de uso, incremento en la precisión en los estimativos de volumen realizados en el campo y un incremento en la disminución de la variación de los estimativos del volumen del huevo. Adicionalmente, nuestra técnica no requiere tiempo de manejo después de la colección de los datos, y no afecta el éxito de eclosión. También, para Rallus longirostris y especies similares, nuestra técnica puede ser combinada con otras técnicas flotación de los huevos) de tal forma que simultáneamente se puedan estimar el volumen del huevo y el estadio embrionario.

Egg mass at laying is an important predictor of hatchling mass in birds. Hatchling mass, in turn, affects reproductive success; smaller eggs produce smaller chicks, and smaller chicks are less likely to survive. Egg mass thus serves as an important measure of parental investment and fitness. Here, McCormick et al determine the egg mass of Glaucous-winged Gulls (Larus glaucescens).

Pigments present in avian eggshells are thought to serve many different adaptive functions. According to the sexually selected eggshell coloration hypothesis, the quantity of pigments in eggshells can serve as a signal of a female’s condition or of her maternal investment into eggs that elicits a higher investment from her partner. Here, we employed a comprehensive approach to test the sexually selected eggshell coloration hypothesis using a cup-nesting passerine with protoporphyrin-pigmented eggshells, the red-backed shrike Lanius collurio , as our model species. We used calibrated digital photography and visual modelling to assess eggshells appearance from an avian point of view. We estimated the condition of chicks and adult females using the Scaled Mass Index and additionally measured average width of growth bars on rectrices of adult females. We quantified the investment of males in terms of provisioning rates to offspring. We found that females in worse condition laid eggs with redder spots and the redness of spots was positively related to the condition of chicks. Visual modelling revealed that males were likely to perceive the variation in colour and brightness among clutches in the studied population, however, the provisioning rates of males were not related to any aspect of eggshell appearance. Thus, while eggshell coloration can act as a cue of female condition, we found no support for the signalling function of eggshell coloration in post-mating sexual selection in the red-backed shrike. Significance statement The amount of pigments that female birds deposit in their eggshells is often related to their condition. For this reason, it has been suggested that eggshell pigmentation can act as an honest indicator of female condition and that it may affect parental investment of their partners. Here, we investigated this hypothesis on the red-backed shrike that lays beige eggs with reddish-brown spots. This species builds cup nests where, unlike in cavities or nest-boxes, light level does not limit ability of males to evaluate the coloration of eggs. Our study revealed that, while eggshell coloration was indeed a cue of female condition, it was not related to the provisioning effort of males to offspring. Therefore, eggshell coloration does not serve the predicted signalling function in the red-backed shrike.

Around the world, declines in the mean size of nesting sea turtles have been reported with concerns of a concomitant decrease in the reproductive output of populations. Here, we explore this possibility using long-term observations of green turtles (Chelonia mydas) at Aldabra Atoll, Seychelles. Based on > 4500 individual measurements over 21 years (1996–2016), we found the curved carapace length of nesting females declined by about 0.64 cm per decade, from 111.43 to 110.08 cm. For 391 individuals that were measured more than once with measurement interval of 2.8–19 years apart, the mean growth rate was 0.14 cm year−1. Comparisons between the size of adult females and males were based on 23 and 14 weight measurements, 107 and 33 carapace length measurements and 103 and 33 carapace width measurements, respectively, taken during 1981–1983. Adult females were larger than males, with the sexual dimorphism index, i.e. the ratio of size of the larger sex to the smaller, being 1.09 and 1.10 for carapace length and width, respectively, and 1.25 for weight. Smaller females tended to lay fewer eggs per clutch but the decrease in female mean size was accompanied by increases in numbers of turtles nesting annually, such that the estimated total numbers of eggs per year increased from 1.3 million to 2.0 million between 1996 and 2016. Therefore, a decrease in mean size of nesting females has not compromised egg production for this population.

Global climate patterns are shifting due to anthropogenic causes, putting pressure on many species that are unable to adapt to such rapid changes. Sea turtle clutches, for example, normally develop between 26 and 33°C, but tolerate higher temperatures at the end of development. High temperatures, protracted rainfall, and droughts have been linked to fewer hatchlings. Likewise, climatic conditions can affect the size of sea turtle hatchlings, which could affect their probability of survival. We analyzed the effects of a biotic factor (egg mass) and environmental factors (precipitation and incubation temperature) on East Pacific leatherback turtle Dermochelys coriacea hatchling sizes in Costa Rica. Hatchling size (mass, straight carapace length, straight carapace width, and head width) was affected by both biotic and environmental factors. While egg mass was the strongest predictor for hatchling mass, temperature was the strongest for carapace length and head width. Carapace width was most strongly predicted by precipitation. Hatchling carapace length and width decreased with increases in temperature and increased with higher levels of precipitation. Hatchling mass also decreased with increasing temperature, although the relationship was not statistically significant. Head width decreased with greater precipitation during development. These findings suggest that increases in temperature and decreases in precipitation may not only decrease the number of hatchlings produced, but may also produce smaller leatherback hatchlings in Pacific Costa Rica, which may impair hatchling survival in the first hours after emergence.

Abstract Nine egg capsules of the Rasptail Skate (Rostroraja velezi) were collected from their southernmost distributional range in northern Peruvian waters for their description. Egg capsules had a glossy black or dark brown color, with a subrectangular shape, slightly wider at posterior end than at anterior end. Egg capsules when observed under a stereoscope revealed a finely striated surface. Egg capsules ranged from 6.8 to 7.7 cm in length, 4.9 to 6.2 cm in maximum width, and 4.2 to 5.9 cm in minimum width. Anterior horn length was shorter than posterior horn length (0.29% vs. 0.58%). Differences in egg capsule surface and size were observed when compared to capsules of R. velezi from Baja California, Mexico, possibly due to differences in environmental conditions since individuals sampled belong to different marine provinces. Our results represent the second study to describe egg capsules for this species and the first in the Tropical Eastern Pacific marine province.