Estudo da biologia reprodutiva de Nycticorax nycticorax no Parque Estadual Fontes do Ipiranga, São Paulo
Resumo
Data on the reproductive biology of birds are essential to test hypotheses regarding the
evolution of different aspects of the life history of these animals. However, basic information
on the reproductive behavior of most South American bird species are poorly known.
Moreover, particularly for birds with wide geographic distribution, life history may vary
according to the different environmental conditions. Thus, the study of reproductive behavior
in different populations of the same species, allow the identification of patterns of variation to
make inferences about the ecological and evolutionary mechanisms responsible for the
diversification and facilitates the development of conservation strategies. The Black Crowned
Night Heron, Nycticorax nycticorax (Ardeidae) is a cosmopolitan species very common in
Brazil, which breeds in large colonies. Although data on the reproductive biology of this
species are available for Europe and North America, is little studied in Brazil. Thus, the
objective of this proposal is to describe the reproductive cycle of N. nycticorax in two
colonies in the Parque Estadual Fontes do Ipiranga, São Paulo, southeastern Brazil. The
breeding season extended from July of 2013 to January 2014, however the field work was
performed from September to January, with peak activity in September. The nests were built
average 3,55 ± 2,58 m high and 2,36 ± 1,62 m alway from the main trunk. A total of 38 nests
were found, but just 29 were monitored. The clutch size was 2.41 ± 0.68 (1 - 3) n = 29, and
the incubation period was 23,26±1,26. The nestlings began to leave the nest with an average
of 17.4 ± 3.6 days of life, what we call the stay 1, and left the nest definitely with 25,71 ± 7,16
days, which we call the residence 2. From 70 eggs, 57.14 % hatched and 25 chicks survived
and left the nest. The survival rate was 31% from laying to the left of the nest, Mayfield. We
compared with other tropical populations and the Northern Hemisphere, we recorded a strong
tendency in latitudinal gradients of larger clutch size at high latitudes, but reproductive
success does not seem to be associated with it, should be more associated with habitat
conditions and availability of resources than with the latitudes. Incubation seem to support the
premise to be higher in tropical regions, but few incubation data and nestling data are
available for comparison.