A Comparison of the Breeding Ecology of Birds Nesting in Boxes and Tree Cavities

Abstract

ABSTI~ICT.-We compared laying date, nesting success, clutch size, and productivity of four bird species that nest in boxes and tree cavities to examine whether data from nest boxes are comparable with data from tree cavities. Western Bluebirds (Sinlin nrexicnnn) gained the mast advantage from nesting in boxes. They initiated egg laying earlier, had higher nesting success, lower predation rates, and fledged marginally more young in boxes than in cavities but did not have laracr clutches or hatch more eggs. Plain Titmice (Pnnis iriorrmtrrs) nesting earlier in boxes. ~oise Wrens (~roglo&tes ~eiion) nesting in boxes laid larger clutches, hatched more eggs, and fledged mare young and had marginally higher nesting success and lower predation rates. Ash-throated Flycatchers (Myinrclirrs cincmscens) experienced no apparent benefits from ncsting in bows versus cavities. No significant relationships were found between clutch size and bottom area or volume of cavities for any of these species. These results suggest that researchers should use caution when extrapolating results from nestbox studies of reproductive success, predation rates, and productivity of cavity-nesting birds. Given the different responses of these four species to nesting in boxes, the effects of the addition of nest boxes on community structure also should be considered. Rrcrived 19 September 1996, nccepted 21 April 1997. NEST BOXES MAY BE USED AS A CONSERVATION