-I examined three factors that may limit the clutch size of the Glaucous-winged Gull (Larus gluucescens) to three or fewer eggs: the energetic cost of egg formation, the shelf-life of eggs, and the incubation capacity of adults. Incubation capacity was found to have a significant effect on the success of large clutches but it cannot explain the absence of 4-egg clutches. Energetic limitation fo...

It has been hypothesized that a high reproductive output contributes to the unique gigantism in large dinosaur taxa. In order to infer more information on dinosaur reproduction, we established allometries between body mass and different reproductive traits (egg mass, clutch mass, annual clutch mass) for extant phylogenetic brackets (birds, crocodiles and tortoises) of extinct non-avian dinosaur...

In a diverse array of avian and mammalian species, experimental manipulations of clutch size have tested the hypothesis that natural selection should adjust numbers of neonates produced so as to maximize the number of viable offspring at the end of the period of parental care. Reptiles have not been studied in this respect, probably because they rarely display parental care. However, females of...

—The majority of the hybrid electric vehicles (HEVs) available on the market are power-split hybrid vehicles with a single planetary gear (PG), including the popular Toyota Prius and Chevy Volt. Although both vehicles use a single PG, they have different configurations with different number of operating modes. The Prius has no clutch and has a single operating mode, whereas the Chevy Volt uses ...

Cooperative breeding is not common in birds but intriguingly over-represented in several families, suggesting that predisposing factors, similar ecological constraints or a combination of the two facilitate the evolution of this breeding strategy. The life-history hypothesis proposes that cooperative breeding is facilitated by high annual survival, which increases the local population and leads...

Double-nesting behaviour, a rare breeding system in which females lay in two nests, one incubated by herself and the other one by her mate, could be considered an intermediate stage in the evolutionary trend from biparental to uniparental care of single clutches. We examined the occurrence and success of double-nesting behaviour in Red-legged Partridges Alectoris rufa in Central Spain. Clutch s...

Parents are selected to preferentially invest in the offspring with highest reproductive value. One mechanism for achieving this is the modification of competitive asymmetries between siblings by maternal hormones. In many organisms, offspring value varies according to birth position in the brood, which determines survival chances and competitive advantage over access to resources. In birds, va...

To study clutch size related energetic costs of incubation, clutch sizes were experimentally manipulated and metabolic rate of female great tits Parus major (L.) during nocturnal incubation (MRinc) was measured with the use of mobile oxygen analysers. Each individual was repeatedly measured, while incubating either reduced, control or enlarged clutches. In contrast to most previous studies, the...

Pathogen infection is typically costly to hosts, resulting in reduced fitness. However, pathogen exposure may also come at a cost even if the host does not become infected. These fitness reductions, referred to as "resistance costs", are inducible physiological costs expressed as a result of a trade-off between resistance to a pathogen and aspects of host fitness (e.g., reproduction). Here, we ...