Avian Communication and Behaviour in Dynamic Environments.

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Behavioural flexibility may enable species to cope with changing or novel environments, which we will investigate among chickadee and sparrow species that have invaded urban areas, expanded their range into novel regions, or come into contact with closely-related (but typically isolated) species. Black-capped, chestnut-backed and mountain chickadees are often attracted to settle in urban greenspace through provision of feeders and nestboxes, but such settlement subjects them to the increased noise levels and altered habitats associated with urbanization. Though these species settle in urban spaces, their capacity to alter vocalizations may affect their ability to compensate for the different environments. Our and other studies show low-frequency urban noise masks lower-pitched vocalizations, which would favour shifts to higher-frequency and louder signals among settling individuals/populations. Black-capped chickadees primarily use long-range songs during spring signalling; mountain chickadees alternate the use of song and shorter-range chick-a-dee calls; and chestnut-backed chickadees lack song and produce only chick-a-dee calls. Using portable speakers broadcasting urban noise, we will test the capacity of males to dynamically adjust their signals to avoid masking, and determine whether the flexibility to adjust differs between species. We will also test the perceptive ability of both females and males to distinguish songs of birds embedded in urban noise, and whether birds that have already settled in urban landscapes produce songs that are less easily masked. Both urban development and forestry practices can also affect likelihood of species interactions. Black-capped and mountain chickadees prefer different habitats and typically do not have overlapping distributions. However, contact sites occur where the lower-altitude deciduous forests (black-capped habitat) abut higher-altitude coniferous forests (mountain habitat), which can arise from land clearing associated with either urbanization or forestry . In one contact population, mountain chickadees (the subordinate species) alter their songs and song/call usage to avoid signal overlap with black-capped chickadees. Despite these adjustments, we found that extra-pair matings between female mountain and male black-capped chickadees resulted in hybrid young appearing in mountain, but not black-capped, nests. We will use genetic analysis to explore the generality of these patterns in new study populations, and determine whether hybrids suffer reduced offspring or adult condition. We will playback mountain chickadee songs to black-capped chickadees to determine whether altering songs is sufficient to reduce aggression from the socially-dominant species. We will also playback black-capped chickadee song bouts within territories of mountain chickadees to determine whether birds dynamically adjust signalling in the presence of a dominant competitor. Logging and dam construction in the northern Rockies have been implicated as the likely source of habitat corridors that have allowed eastern species, like white-throated sparrows, to establish small breeding populations in north central British Columbia. This small western population of sparrows sings a distinctive dialect from the common song heard throughout eastern Canada, and may result from founder effects of this western population coupled with behavioural learning of songs. We will use a combination of genetic analyses, distinctive isotope levels in feathers and light-sensing geolocator backpacks mounted on migrating birds to determine the degree to which populations on either side of the Rockies are isolated, and how this affects the evolution and spread of song dialects in this peripheral population.