No abstract

The breeding biology of the little egret ( Egretta garzetta ) was studied in 20 nests within the mixed-species breeding colonies at Nanchong, Sichuan, Southwest China, in 2006. By measuring a set of physical characteristics of vegetation at the nests and at a set of 20 randomly chosen sites we showed that birds preferentially used taller trees in areas with fewer shrubs of higher species diversity. Nests at lower locations in trees had marginally lower hatching success due to their destruction by humans; this destruction contributed marginally significantly to lowering of the total nesting success in all studied nests. Although gale winds also had a negative effect on breeding success, the anthropogenic influences were a greater factor in reproductive failure. We found similar effects in our review of literature on breeding success of the little egret from various geographical areas. Our results may be of use by conservation organizations in their actions to protect colonies of the little egret.

No abstract

In organisms with complex life cycles, such as amphibians, morphological variation itself is strongly influenced by environmental factors and maternal effects. Although temperature and food level exert a strong influence on larval growth and development, little is known about the interacting effects of these factors on age and size at metamorphosis. In this study, plasticity in growth rates, larval mass, larval period, and body size at metamorphosis were experimentally examined for a high-altitude toad (Bufo minshanicus) under different combinations of temperature and food level. Larval period and mass at metamorphosis were sensitive to food level, and varied with temperature. At high food level, tadpoles reared at 29.8°C had shorter larval period lengths and larger mass at metamorphosis than those reared at 25.8 and 22.6°C, but not between 25.8 and 22.6°C. Interestingly, tadpoles at 29.8°C that were offered with a higher level of food supply achieved a larger size than those with a lower level of food supply; however, food supply did not affect body mass at the two lower temperature settings. Thus, the effects of food level were dependent on water temperature. Although there was high mortality at 29.8°C, surviving tadpoles have been much stronger to achieve faster growth and reach a larger mass at metamorphosis, which were positively correlated with juvenile survival and adult fecundity. Thus, under varied environmental conditions, we could say that there is more plasticity in development and growth of larvae in high altitude populations than in the same species or other species from low altitude populations.

Typically, anuran amphibians favor larger females as mates because larger females lay more eggs; thus, males in amplexus can increase the number of eggs fertilized, and fitness. However, males may also prefer those females that were closest to the norm for their population in overlapping populations, and these individuals do not receive the benefits of enhanced fertilization success. In this study, we test how male Bufo gargarizans choose mates in the presence and absence of an invasive species, bullfrogs {Rana catesbeiana). When given a simultaneous choice between a small male and a large female toad, males discriminated between the sexes and attempted to clasp a large female. However, when one male toad was presented with a large female bullfrog and a small female toad, the males chose both with equal frequency. Therefore, male B. gargarizans appears to trade-off between species and mate-quality recognition, such that those toads co-occurring with heterospecifics do not blindly prefer mate-quality to ensure conspecific matings.