Chimango: are you going to eat that?
One of the raptor species studied by the scientists at CECARA, is the chimango caracara (Milvago chimango). Chimangos are medium sized raptors, in which both males and females bear brownish plumages. The main difference between them is that males exhibit conspicuous yellow ceres (in the bill and tarsus), that are duller in females (Fig 1). Chimangos can be found in a wide array of habitats, from coastal areas to the mountains. In addition, chimangos are also found in urban and peri-urban environments where they usually take advantage of humans when looking for nesting sites or food.
Figure 1: Female (left) and male (right) chimango.
In one of these peri-urban populations is where the researchers of the CECARA usually work. This population is located at about 10 km from Santa Rosa, in a residential area where there are many trees used by the chimangos to breed (Fig. 2). During my time in Santa Rosa I took part in many of the interesting studies conducted in this population, from population dynamics to behavioural ecology and conservation.
Figure 2: Male chimango inside his nest in a caldén (Prosopis caldenia)
For me, one of the most interesting aspects of the chimangos is their behavioral plasticity, and their ability to maximize the available resources, especially when it comes to diet. During fieldwork I was able to record chimangos eating very different things (Fig. 3), caterpillars, shrimp, carrion, rodents, fish or food waste. I am amazed by this and by the remarkable ability of this species to feed on such a variety of things, evidencing the huge “intelligence” of this species.
Figure 3: Chimangos with different food items. From left to right and up to down: fish (Odontesthes bonariensis), cuis (Microcavia australis), shrimp, caterpillars and a chicken wing,
However, the intelligence of these birds when it comes to their diet does not manifest when we look to their “breeding abilities”. In this population there is a really big nest failure, approximately in 45% of the nest the eggs do not hatch. This is in part really surprising, as the breeding conditions of this population seem rather perfect. There is plenty of food available and not many natural predators as the populations is in-between a human settlement. To this day we do not know the factors that explain why there are some many failures in the nest of the chimangos. One hypothesis is that the cats that inhabit in the urbanization are the main predators of the nests. Its rather paradoxical that the chimangos obtain so many advantages from humans in terms of food, or breeding sites, when humans are the ultimate responsible of their reduced breeding success as they do not properly control their cats. More research needs to be conducted, however, to elucidate the role of cats and other factors in the nest failure of this population.
David López-Idiáquez (5 - March, 2019)