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Understanding the role of diet in the physiological condition of adults during reproduction and hence its effect on reproductive performance is fundamental to understand reproductive strategies in long-lived animals. In birds, little is known about the influence of the quality of food consumed at the beginning of the reproductive period and its short-term effects on reproductive performance. To assess the role of diet in the physiological condition of female blue-footed booby, Sula nebouxii (BFBO), during reproduction we evaluated whether individual differences in diet (assessed by using δ13C and δ15N values of whole blood from female birds and muscle tissue of the principal prey species) prior to egg laying and during incubation influenced their lipid metabolic profile (measured as triglyceride levels and C:N ratio) and their reproductive performance (defined by laying date, clutch size and hatching success). Females with higher δ15N values in their blood during the courtship and incubation periods had a higher lipid metabolic profile, earlier laying date, greater clutch size (2–3 eggs) and higher hatching success. Females that laid earlier and more eggs (2–3 eggs) consumed more Pacific anchoveta (Cetengraulis mysticetus) and Pacific thread herring (Opisthonema libertate) than did other females. These two prey species also had high amounts of lipids (C:N ratio) and caloric content (Kcal/g fresh weight). The quality of food consumed by females at the beginning of reproduction affected their physiological condition, as well as their short-term reproductive performance. Our work emphasizes the importance of determining the influence of food quality during reproduction to understand the reproductive decisions and consequences in long-lived animals.

This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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In long-lived monogamous social species, partner compatibility can play a crucial role in reproductive success. We evaluated assortative mating based on body condition (plasma triglyceride concentration), diet (δ 15 N), and foraging habitat (δ 13 C) in the blue-footed booby Sula nebouxii, a long-lived monogamous seabird. We investigated the effects of assortative mating (sum of triglycerides in a pair) and asymmetry within pairs (residuals from regression of female-male triglycerides) on reproductive performance and offspring growth (alkaline phosphatase, ALP). We found that strong assortative mating determined by body condition and diet seemed to be related to a signalling mechanism (nutritional state). This mating pattern had a substantial effect on the breeding parameters and influenced offspring ALP. Within-pair asymmetry did not influence any reproductive parameters, but the ALP of offspring was related to the within-pair relative female condition. Overall, our results indicate that individuals seek the best possible match to maximize their breeding investment and/or individuals are limited in their mate options by their current body condition, which has consequences for offspring fitness in the short term. Our findings show that assortative mating based on body condition produces notable variation in the joint condition of the pair, which determines their breeding success.

Songbirds are one of the groups most vulnerable to extreme heat events. Although several recent studies have assessed their physiological responses to heat, most of them have focused on arid-zone species solely. We investigated thermoregulatory responses to heat in eight small-sized songbirds occurring in the Mediterranean Basin, where heatwaves are becoming more frequent and intense. Specifically, we determined their heat tolerance limits (HTL) and evaporative cooling efficiency and evaluated their current and future vulnerabilities to heat in southwestern Iberia, a Mediterranean climate warming hotspot. To do this, we exposed birds to an increasing profile of air temperatures (Ta) and measured resting metabolic rate (RMR), evaporative water loss (EWL), evaporative cooling efficiency (the ratio between evaporative heat loss and metabolic heat production) and body temperature (Tb). HTL ranged between 40 and 46°C across species, and all species showed rapid increases in RMR, EWL and Tb in response to increasing Ta. However, only the crested lark Galerida cristata achieved an evaporative cooling efficiency greater than 1. The studied songbirds currently experience summer Ta maxima that surpass their upper critical temperatures of their thermoneutral zone and even their HTL. Our estimates indicated that five of the eight species will experience moderate risk of lethal dehydration by the end of the century. We argue that the limited heat tolerance and evaporative cooling efficiency of small-sized Mediterranean songbirds make them particularly vulnerable to heatwaves, which will be exacerbated under future climate change scenarios.

El phytohaemagglutinin (PHA) se prueba para medir la inmunidad adquirida y es uno de los métodos más utilizados; actualmente, está siendo debatido a raíz de los nuevos conocimientos sobre la compleja fisiología del proceso. Como respuesta secundaria reiterada a los mayores desafíos vinculados a los aumentos de los niveles de linfocitos T circulantes sería indicativo de una respuesta inmune mediada por células, se realizó por primera vez un experimento bajo condiciones naturales con repetidas PHA desafíos en libre-viviendo los pájaros adultos y polluelos para arrojar luz sobre este tema. Hemos encontrado significativamente más fuerte respuesta a PHA inyección secundaria independiente del sexo o la edad, mientras que el control de la condición corporal, la segunda respuesta es en promedio 90% más grande que el primero. Igualmente, los recuentos de linfocitos fueron significativamente superiores en el segundo reto de PHA, mientras que no se encontraron diferencias significativas entre las aves no tratadas. Las correlaciones positivas significativas entre la PHA respuesta y ambos recuentos de linfocitos y los niveles de proteínas plasmáticas (principalmente albúmina, globulina (precursor) fueron recuperados, mientras que no hubo diferencias significativas en los niveles de proteínas plasmáticas recuperados entre los retos. Nuestros resultados son consistentes con las aves cautivas, apoyando la validez del PHA de la hinchazón de la piel como prueba precisa de haber adquirido células T como la inmunidad en aves.The validity of using the phytohaemagglutinin (PHA) test to measure acquired immunity, one of the most widely used methods, is currently being debated due to new knowledge on the complex physiology of the process. As a greater secondary response to repeated challenges linked to increases of circulating lymphocyte levels would be indicative of a T-cell-mediated immune response, we performed for the first time an experiment under natural conditions with repeated PHA challenges in free-living adult birds and chicks to shed light on this topic. We found significantly stronger secondary response to PHA injection independent of sex or age, while controlling for body condition, the second response being on average 90% larger than the first. Likewise, lymphocyte counts were significantly higher in the second PHA challenge, whereas no significant differences were found among untreated birds. Significant positive correlations between the PHA response and both lymphocyte counts and plasma protein levels (mainly albumin, globulin (precursor) were recovered, whereas no significant differences were recovered in plasma protein levels between challenges. Our results are consistent with those from captive birds, supporting the validity of the PHA skin-swelling test as an accurate gauge of acquired T-cell-mediated immunity in birds.Trabajo patrocinado por: Fondo Mejicano para Conservación de la Naturaleza. Proyecto PIE 2012 A-P-C-IGSI-12-12 Gobierno de Extremadura. CONACYT (I010/176/2012) y becas PO10014 y RE12002 Go...