ABSTRACT. Egg volumes are most often estimated using a mathematical model that incorporates length and width measurements and a species-specific shape variable. Although adequate in many respects, this technique does not account for intraspecific variation in egg shape. We developed a computer-automated technique that uses calibrated digital photographs to render precise measurements of several egg-size parameters including length, width, volume, and surface area. The system extracts egg outlines from photographs, and divides each egg into latitudinal slices that are subsequently regarded as simple geometric shapes (cylinders or cone frustra) with volumes and surface areas that can be summed to generate size parameters for the entire egg. We tested this technique using 491 eggs from Florida Scrub-Jay (Aphelocoma coerulescens) nests and compared the resulting egg volumes with volumes calculated using the preeminent method of estimating volume from linear measurements. Our method was highly accurate, and differences between the volumes from our method and the alternative method were strongly associated with variation in egg shape. Advantages of our technique include decreased handling of eggs and increased accuracy. Software resources and additional information regarding the technique are available at http://www.archbold-station.org/abs/data/birddata/Bridge-JFO-eggsize.htm. SINOPSIS. Medidas de huevos utilizando fotografía digital: poniendo a pruebas el método de Hoyd con huevos de Aphelocoma coerulescensEl volumen de los huevos comunmente es estimado utilizando un modelo matemático en donde se incorpora el ancho y el largo del huevo y la variable de la forma de este. Aunque es un método adecuado en muchos aspectos, esta técnica no toma enconsideracion las variaciones intraespecificas de la forma de los huevos. Desarrollamos una técnica automática con computadora, que usa fotografia digital calibrada para ofrecer medidas de los huevos incluyendo largo, ancho, volumen yárea superficial. El sistema extrae parámetros de los huevos de fotografías y divide cada huevo en rebanadas latitudinales, que subsecuentemente son tomadas como formas geométricas (e.g., cilindros o conos) con volumenes yáreas superficiales, que a su vez pueden ser utilizadas para obtener el largo y el ancho. Pusimos a prueba esta técnica con 491 huevos del Azulejón (Aphelocoma coerulescens) y comparamos el volumen de los huevos obtenidos con el computador con volumenes calculados con el método usual de medidas lineales. Nuestro método fue preciso y las diferencias en los volumenes usando nuestro método y las del método clásico estuvieron asociadas a la variación en la forma de los huevos. Entre las ventajas de nuestra técnica encontramos una disminución en la manipulación de los huevos y un aumento en la presición de los datos tomados. Los recursos computacionales que se necesitan e información adicional sobre esta técnica se encuentra disponible en: http://www.archbold-station.org/abs/data/birddata/Bridge-JFO-eggsize.htm.

For many animals, adult size is an important determinant of fitness. Thus, after a period of food restriction, offspring often grow quickly to approach an optimal size. Offspring can approach an optimal size by increasing mass faster than the peak growth of offspring that do not delay development (compensatory growth) or by extending the period of rapid growth to reach an optimal size (catch-up growth). Unfortunately, the most common statistical techniques make it difficult to differentiate alternative growth patterns among developing offspring. Here, I show how random effect estimates can be used to uncover important variation in growth in a short-lived passerine, the House Sparrow Passer domesticus. Specifically, I show that much of the variation in offspring growth can be explained by differences in the timing of peak growth and in final adult size, both within a single population and within treatments of an experimental manipulation. These results suggest that much of the variation in offspring growth may be explained by factors other than growth rate. I also show that offspring that delay development either maintain slow but steady growth across development and reach a small adult size, or extend the period of rapid growth to reach an optimal size, indicative of catch-up growth. This pattern of extending the period of rapid growth may allow offspring to minimize the cellular damage caused by compensatory growth but still maximize size-related fitness benefits (e.g. increased survival and fecundity) prior to fledging.

Hatching failure occurs in approximately 10% of all avian eggs, but varies both within and among species. This reduction in viable offspring can have significant fitness consequences for breeding parents; therefore, it is important to understand which factors influence variation in hatching failure among populations. Previous research suggests that hatching failure is higher in a suburban than in a wildland population in the Florida scrub‐jay. From 2003 to 2007, we performed two experiments to examine whether increased hatching failure in the suburbs resulted from 1) increased length of off‐bouts during incubation (predation risk hypothesis, 2003–2004) or 2) increased exposure to ambient temperature during laying (egg viability hypothesis, 2005–2007). Hatching failure was higher for females that took fewer off‐bouts, but the length of those off‐bouts did not influence hatching failure. Thus, nest predation risk does not appear to explain higher hatching failure in the suburbs. Alternatively, hatching failure increased with increasing exposure of eggs to ambient conditions during the laying period. First‐laid eggs in the suburbs had the greatest pre‐incubation exposure to ambient temperature and the greatest rate of hatching failure, consistent with the egg viability hypothesis. Urbanization influences hatching failure through a series of complex interactions. Access to predictable food sources advances mean laying date in suburban scrub‐jays, leading to larger clutch sizes. Because scrub‐jays begin incubation with the ultimate egg, first‐laid eggs in the suburbs may be exposed to ambient temperatures for longer periods, thus reducing their viability.

The NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. In many vertebrates parental age is related to reproductive output with older individuals 25 often performing better (e.g., advanced timing, more offspring) than younger ones. First-26 year birds differ from older birds in that they lack previous experience with the 27 reproductively-stimulatory effects of long day lengths (photostimulation). The goal of this 28 study was to examine whether this age-related increase in reproductive output can be 29 attributed, at least in part, to previous experience with photostimulation in a 30 photoperiodic bird, the female house finch (Carpodacus mexicanus). Specifically, we 31 investigated whether previous experience with photostimulation influences the early 32 stages of reproductive development by quantifying plasma luteinizing hormone (LH), 33 plasma vitellogenin, ovarian follicle size, and immunoreactivity of hypothalamic 34 1 Prior Experience with Photostimulation Enhances Photo-Induced gonadotropin-releasing hormone (GnRH-I) and vasoactive intestinal polypeptide (VIP). 35By differentially manipulating photoperiod, we generated two groups of first-year female 36 finches: a photo-experienced group that had been through one photoperiodically-37 induced cycle of gonadal development and regression, and a photo-naïve group 38 exposed to long days since hatch. Both groups were then transferred from long to short 39 days for nine weeks, to ensure full photoperiodic responsiveness, and then 40 photostimulated for four weeks and exposed to conspecific or heterospecific male song 41 starting 90 minutes before sacrifice. Following photostimulation, although photo-42 experienced and photo-naïve groups exhibited similar surges in plasma LH 43 concentrations, circulating vitellogenin levels increased in photo-experienced, but not in 44 photo-naïve birds. After four weeks of photostimulation, egg yolk deposition was 45 observed in two of six photo-experienced birds but in none of the photo-naïve birds. 46 3 After four weeks of photostimulation and exposure to conspecific or heterospecific male 47 song, more GnRH-I-ir cells were seen in the septo-preoptic hypothalamus of photo-48 experienced than of photo-naïve birds. In contrast, there were no differences between 49 the photo-experienced and photo-naïve birds, irrespective of the song type they were 50 exposed to, in numbers of visible VIP-ir cells in the mediobasal hypothalamus. Our 51 results demonstrate that previous photo-experience enhances some of the early stages 52 of photo-induced reproductive development, and that the reproductive neuroendocrine 53 system of photo-experienced, photoperiodic birds is primed to respond rapidly to 54 reproductively-stimulatory environmental and social cues. 55

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