{'fraction_non_alphanumeric': 0.030355594102341718, 'fraction_numerical': 0.022549869904596703, 'mean_word_length': 5.204301075268817, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Extreme Between-Year Variation in Productivity of a Bridled Titmouse (Baeolophus wollweberi) Population

Abstract Environmental variability affects life-history decisions such as allocation of resources to reproduction. However, in the case of small passerine birds, pairs that acquire a territory do not usually skip a breeding season. This study presents breeding-success data from two contrasting years for a population of Bridled Titmice (Baeolophus wollweberi). During an El Niño year (1998), 20 pairs attempted to breed, and 85% were successful. Survival of juveniles from 10 banded broods through nutritional independence was 100%, excluding one depredated nest. Breeding success was much lower in the following La Niña drought year. Fifty-seven pairs established territories in the study area. Twenty-seven never progressed to nest building. Thirteen pairs were successful; survival of young from banding to nutritional independence was 41.4%. An average of 0.47 fledglings per breeding pair was produced in 1999, compared to 4.40 the previous El Niño year. This study examines possible adaptive significance of forgoing breeding in a poor year.