Variable effect of playback of chickadee mobbing calls on detection probability of boreal forest birds

Abstract

Modification of the point count survey method to include playback of songbird mobbing calls in an attempt to increase detection probabilities has met with mixed success. We compared detection probabilities for boreal forest songbirds using traditional point count methods and counts using broadcasts of the mobbing calls of Black-capped Chickadees (Poecile atricapillus) in an attempt to increase detection probability. We conducted 594 point counts during the 2010 breeding season in Newfoundland, Canada. Each point count consisted of an 8-min silent observation period followed by an 8-min broadcast of Black-capped Chickadee mobbing calls. Occupancy model results showed that response to playback broadcast varied across species, with detection probabilities higher for seven of 17 species during the silent portions of point counts and three species more likely to be detected during playback intervals. For all species, the number of visual detections increased during periods of playback and, averaged across species, individuals were >6 times more likely to be seen during the playback period than during the silent period. Differences in detection probability among observers were apparent during both silent and playback periods. We suggest that using playback of chickadee mobbing calls during point count surveys of common boreal forest songbird species may be most beneficial when visual detection is important. However, playback may also be useful for species-specific surveys during periods when birds are less likely to be vocal or for studies of less common species with chronically low detection probabilities. A combined silent and playback approach could also be useful, although observer and species differences should be accounted for if comparing data across species or studies. RESUMEN. Efecto variable de las grabaciones de conducta de turbas en Poecile atricapillus, en la probabilidad de detectar aves en un bosque borealModificaciones en los conteos de puntos, para incluir grabaciones de llamadas de turbas, en el intento de incrementar las probabilidades de detección de aves han tenido resultados mixtos. Comparamos la probabilidad de detección para aves en bosques boreales, utilizando conteos de puntos tradicionales y llamadas de turbas del Carbonero Cabecinegro (Poecile atricapillus), en un intento de incrementar la probabilidad de detección de aves. Se condujeron 594 conteos de puntos durante el periodo reproductivo del 2010, en Newfoundland, Canadá. Cada punto consistió de 8 minutos de observación en silencio, seguido de 8 minutos de una grabación de la llamada de turba del Carbonero Cabecinegro. El modelo utilizado mostró que la respuesta a las grabaciones varía entre especies, con una alta probabilidad de detección de siete de 17 especies durante los periodos de silencio y de tres especies adicionales durante la exposición a grabaciones. Para todas las especies, el número de detecciones visuales incrementó durante los periodos de uso de grabaciones y el promedio entre todas estas, resultó con una probabilidad seis...

Gray-cheeked Thrush (Catharus minimus minimus) distribution and habitat use in a montane forest landscape of western Newfoundland, Canada

“…m, but other bird surveys in the region complement our data in terms of the elevational range covered. During a study by Rae et al (2015) at elevations ranging from 4 to 400 m in Gros Morne National Park, which is situated on the west slope of the Long Range Mountains ~40 km west of our study area, this species was detected at just 5 of 596 point counts (0.8%). In contrast, in 2014 fourteen territorial thrushes were observed nearby at elevations of 450-600 m along a 10-km route in the park highlands (Darroch M. Whitaker, unpublished data).…”

“…Surveys were conducted between 0530 and 1700 h each day and ran from the first week of June until the third week of July each year. To increase the likelihood of observing birds, we used playbacks of Black-capped Chickadee (Poecile atricappillus) predator mobbing calls as well as conspecific song and vocalizations of all seven focal species (Gunn et al 2000, Betts et al 2005, Rae et al 2015. Gray-cheeked Thrushes are furtive and erratic in their singing and calling (Lowther et al 2001, Marshall 2001, and this approach can be useful for increasing visual detections of such species and also for reducing variation in detection rates associated with time of day or time of season (Rae et al 2015;Darroch M. Whitaker, unpublished data).…”

“…To increase the likelihood of observing birds, we used playbacks of Black-capped Chickadee (Poecile atricappillus) predator mobbing calls as well as conspecific song and vocalizations of all seven focal species (Gunn et al 2000, Betts et al 2005, Rae et al 2015. Gray-cheeked Thrushes are furtive and erratic in their singing and calling (Lowther et al 2001, Marshall 2001, and this approach can be useful for increasing visual detections of such species and also for reducing variation in detection rates associated with time of day or time of season (Rae et al 2015;Darroch M. Whitaker, unpublished data). On arriving at a station, an observer silently looked and listened for birds for one minute and then broadcast a series of bird recordings that began with a five-minute recording of chickadee predator mobbing calls followed by a series of two-minute recordings of each focal species' calls and territorial song, ending with Gray-cheeked Thrush.…”

“…On arriving at a station, an observer silently looked and listened for birds for one minute and then broadcast a series of bird recordings that began with a five-minute recording of chickadee predator mobbing calls followed by a series of two-minute recordings of each focal species' calls and territorial song, ending with Gray-cheeked Thrush. The volume control of broadcasting units was set at a constant level for all surveys, and when measured 1 m from the speaker the average volume of chickadee playbacks was 81.5 dB, with peak volumes of 92.7 dB (see also Rae et al 2015). Use of conspecific playbacks is a strong attractant for territorial songbirds, especially males, during the breeding season (Betts et al 2005).…”

An improved survey method for monitoring population trends of Golden‐winged Warblers and other patchily distributed birds

“…88,No. 4 Similarly, Rae et al (2015) found that broadcasts of the mobbing calls of Black-capped Chickadees had highly variable effects on detectability across 17 species of boreal-forest birds in Canada, but that visual detections averaged six times more likely during the mobbing-broadcast period. Visual detection and confirmation of Golden-winged Warblers is an important component of our survey because Golden-winged Warblers, Blue-winged Warblers, and hybrids can sing similar songs or imitate each other's songs (Confer et al 2011), making species-level identifications problematic based on only auditory cues.…”