Mixed species flocks of birds as strategy: Behavior and seasonality in Yungas Foothill of North-West, Argentina

MANGINI G. GISELLE; ARETA JUAN IGNACIO; FACUNDO ARIEL GANDOY

Puerto Iguazu

Congreso; Ornithological congress of the Americas; 2017

Although it has been long recognized that mixed flocks in temperate forest are seasonal and in tropical forest are annual, seasonality of mixed flocks in the middle-term Subtropical forest of Argentina remains inconclusive as well as the climatic elements that trigger flocking behavior in birds. We surveyed the number of mixed flocks, the number of species and the number of individuals in mixed flocks over 3 years in the Yungas foothill of NorthWest Argentina to examine seasonality of mixed flocks and birds flocking behavior in response to changes in temperature, humidity, and fragmentation in order to test the hypotheses that birds flock more frequently under harsh conditions. Mixed flocks followed a seasonal pattern and the peak was on dry season (April-September). Harsh conditions lead to flocking, as temperature and humidity decreased more and bigger mixed flocks were recorded between and within seasons. Bird responses to climatic elements and seasonality of mixed flocks were similar in both type of forest configuration. However, forest fragments had fewer and smaller mixed flocks due to the low number of bird species and individuals recorded that could form mixed flocks in them. Collectively seasonal pattern, bird responses to climatic elements and to fragmentation suggest that birds form mixed flocks more frequently under harsh conditions and this result is probably linked to the benefits that birds gain by forming mixed flocks.