Fire in the boreal forest: Proximate effects on reproduction and long-term consequences for territory occupancy of American kestrels

Abstract

:There is currently a great deal of interest in documenting habitat use of birds in the boreal forest, especially in response to disturbances such as harvesting and forest fires. Studies have shown that some avian species are much more common in recently burned areas, whereas others are absent. Despite this, we know little about the immediate effect of a large forest fire, and its considerable alteration of habitat, on birds during a single breeding season. In 1995, a 72,000-ha forest fire in our study area gave us the opportunity to assess the effects of fire on reproduction of American kestrels (Falco sparverius) in comparison to an adjacent control area. In addition, we also examined territory occupancy by kestrels in the burned and control areas 8 y following the fire. We found no immediate effect of the fire on body condition of adult kestrels, their ability to hatch eggs, or to fledge at least one young. Birds breeding in the area that burned, however, did fledge fewer offspring per nest, and these nestlings had reduced body mass compared to control nests, possibly because of an immediate reduction in available prey following the fire. Nonetheless, given the profound alteration of habitat following the fire, the fact than any birds remained to continue breeding is remarkable. Territory occupancy of the burned area in 2003 was similar to 1995, the year of the fire, but occupancy in the adjacent control area declined during this period. It therefore appears that the control area is becoming a less suitable habitat for kestrels as the forest continues to mature, whereas the burned area is still providing viable habitat for kestrels. We present evidence suggesting that some of the differences in occupancy between the control and burned area may be due to fewer nest predators in the burned area in 2003.