Data for the Big Boom Theory: the Common Nighthawk wing-boom display delineates exclusive nesting territories

Understanding the functional significance of bird sounds can provide
valuable insight into behavior and how birds use habitat. We show that the
Common Nighthawk wing-boom display is a territorial signal associated with
the nest location that can be used to identify territorial habitat use. In
other words, the Common Nighthawk wing-boom display can be considered
analogous to song due to its potential function in territoriality. We
captured, tagged, and tracked 21 male Common Nighthawks in northeastern
Alberta to confirm the functional significance of the wing-boom display
and describe Common Nighthawk territoriality. Mean wing-boom use density
(hereafter “area") size was 10.2 ha (SD=11.7 ha). We found minimal
overlap in wing-boom area (5 of 15 neighboring male pairs, 0.2%-4.5%
overlap), suggesting the wing-boom display represents an exclusive
territory. Comparison of wing-boom locations and random points within the
wing-boom area confirmed that male Common Nighthawks select areas near the
nest to perform wing-boom displays. There was high wing-boom area overlap
for the same individual between years. Differences between years reflected
shifts in nest location, suggesting that the wing-boom display is a good
indicator of the nest location and territory. Future Common Nighthawk
surveys should record the type of acoustic signal observed to
differentiate territorial and nesting habitat use. Many taxa that produce
non-vocal sounds as part of breeding displays could similarly benefit from
a functional classification of song to provide insight into habitat use.