Species-Specific Responses of Bird Song Output in the Presence of Drones

Drones are now widely used to study wildlife, but their application in the study of bioacoustics is limited. Drones can be used to collect data on bird vocalizations, but an ongoing concern is that noise from drones could change bird vocalization behavior. To test for behavioral impact, we conducted an experiment using 30 sound localization arrays to track the song output of 7 songbird species before, during, and after a 3 min flight of a small quadcopter drone hovering 48 m above ground level. We analyzed 8303 song bouts, of which 2285, from 184 individual birds were within 50 m of the array centers. We used linear mixed effect models to assess whether patterns in bird song output could be attributed to the drone’s presence. We found no evidence of any effect of the drone on five species: American Robin Turdus migratorius, Common Yellowthroat Geothlypis trichas, Field Sparrow Spizella pusilla, Song Sparrow Melospiza melodia, and Indigo Bunting Passerina cyanea. However, we found a substantial decrease in Yellow Warbler Setophaga petechia song detections during the 3 min drone hover; there was an 81% drop in detections in the third minute (Wald test, p < 0.001) compared with before the drone’s introduction. By contrast, the number of singing Northern Cardinal Cardinalis cardinalis increased when the drone was overhead and remained almost five-fold higher for 4 min after the drone departed (p < 0.001). Further, we found an increase in cardinal contact/alarm calls when the drone was overhead, with the elevated calling rate lasting for 2 min after the drone departed (p < 0.001). Our study suggests that the responses of songbirds to drones may be species-specific, an important consideration when proposing the use of drones in avian studies. We note that recent advances in drone technology have resulted in much quieter drones, which makes us hopeful that the impact that we detected could be greatly reduced.

Species-Specific Responses of Bird Song Output in the Presence of Drones

Drones are now widely used to study wildlife, but applications for studying bioacoustics have been limited. Drones can be used to collect data on bird vocalizations, but an ongoing concern is that noise from the drones could change bird vocalization behavior. To test this behavioral impact we conducted an experiment using 30 sound localization arrays to track the song output of seven songbird species before, during, and after a 3-minute flight of a small quadcopter drone hovering at 50 m above ground level. We analyzed 8,303 song bouts, of which 2,285 song bouts of 184 individual birds were within 50 meters of the array centers. We used linear mixed effect models to assess patterns in song output showed patterns that could be attributed to the drone’s presence. We found no evidence of any effect of the drone for five species: American Robin Turdus migratorius, Common Yellowthroat Geothlypis trichas, Field Sparrow Spizella pusilla, Song Sparrow Melospiza melodia, and Indigo Bunting Passerina cyanea. However, we found a substantial decrease in Yellow Warbler Setophaga petechia song detections during the 3-minute drone hover, such that there was an 81% drop in detections in the 3rd minute (Wald-test, p<0.001), compared with before the drone’s introduction. In contrast, the number of singing Northern Cardinal Cardinalis cardinalis increased after the drone was introduced, and remained almost five-fold higher for 4-minutes after the drone departed (P<0.001). Further, we found an increase in cardinal contact/alarm calls when the drone was overhead, with the elevated calling-rate sustaining for 2 minutes after the drone had departed (P<0.001). Our study suggests that responses of songbirds to drones may be species-specific, an important consideration when proposing the use of drones in avian studies. We note that recent advances in drone technology have resulted in much quieter drones, which makes us hopeful that the impacts that we detected could be greatly reduced.

New feather mites of the genus Amerodectes Valim and Hernandes (Acariformes: Proctophyllodidae) from passerines (Aves: Passeriformes) in Georgia, USA

Eight new species of the feather mite genus Amerodectes Valim and Hernandes, 2010 (Proctophyllodidae: Pterodectinae) are described from passerines (Aves: Passeriformes) in Georgia, USA: Amerodectes cathari sp. n. from Catharus ustulatus (Nuttall) (Turdidae), A. haemorhous sp. n. from Haemorhous mexicanus (Muller, PLS) (Fringillidae), A. helmitheros sp. n. from Helmitheros vermivorum (Gmelin) (Parulidae), A. hribari sp. n. from Geothlypis trichas (Linnaeus) (Parulidae), A. hylocichlae sp. n. from Hylocichla mustelina (Gmelin) (Turdidae), A. passerinae sp. n. from Passerina ciris (Linnaeus) (Cardinalidae), A. seiurus sp. n. from Seiurus aurocapilla (Linnaeus) (Parulidae), and A. spizellae sp. n. from Spizella passerina (Bechstein) (Emberizidae). An updated world checklist of Amerodectes species and a key to species recorded and potentially expected in North America (USA and Canada) are proposed.

Fluctuations in neighbourhood fertility generate variable signalling effort

Studies of sexual signalling generally focus on interactions between dyadic pairs, yet communication in natural populations often occurs in the context of complex social networks. The ability to survey social environments and adjust signal production appropriately should be a critical component of success in these systems, but has rarely been documented empirically. Here, we used autonomous recording devices to identify 118 472 songs produced by 26 male common yellowthroats ( Geothlypis trichas ) over two breeding seasons, coupled with detailed surveys of social conditions on each territory. We found strong evidence that common yellowthroat males adjusted their total song production in response to both changes in within-pair social context and changes in the fertility of neighbouring females up to 400 m away. Within the social pair, males drastically reduced their song production when mated, but the magnitude of this reduction depended on both the time of day and on the fertility status of the social mate. By contrast, when fertile females were present on nearby territories, males increased their song output, especially during daytime singing. At this time, it is unclear whether males actively gathered information on neighbouring female fertility or whether the patterns that we observed were driven by changes in social interactions that varied with neighbourhood fertility. Regardless of the mechanism employed, however, subtle changes in the social environment generated substantial variation in signalling effort.

Songbird-transported tick Ixodes minor (Ixodida: Ixodidae) discovered in Canada

Ticks are carried into Canada by millions of birds during spring migration, and some of these blood-sucking ectoparasites harbour tick-associated pathogens. During a pan-Canadian study of ticks on avian hosts, we identified an extralimital tick, Ixodes minor Neumann (Ixodida: Ixodidae) collected from a Common Yellowthroat, Geothlypis trichas (Linnaeus) (Passeriformes: Parulidae) at Toronto, Ontario, Canada. Although the I. minor larva was not tested for any tick-borne pathogens, this tick species is considered a competent enzootic vector of the Lyme disease spirochete, Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt, and Brenner sensu lato (s.l.). Epidemiologically, diverse B. burgdorferi s.l. genospecies have been detected in, or isolated from I. minor, and this tick species potentially represents a public health risk not only in the southeastern United States of America, where I. minor is indigenous, but also in Canada. This tick collection is the northernmost report of I. minor in North America, and constitutes the first documentation of this tick species in Canada.