Risk allocation: acute and chronic predator exposure have contrasting effects on Song Sparrow (Melospiza melodia) singing behaviour

Abstract

Increasing the danger posed by predators may cause prey animals to alter their behaviour. For example, they may be more vigilant and so feed more slowly. Breeding male Song Sparrows (Melospiza melodia (A. Wilson, 1810)) spend much time in conspicuous, loud song, which is an important behaviour for territorial defense and for mate attraction. We measured their singing behaviour in relation to both chronic (active Cooper’s Hawk (Accipiter cooperii (Bonaparte, 1828)) nest nearby) and acute (playback of hawk calls) predator exposure. We found that proximity to a Cooper’s Hawk nest had little or no influence. In contrast, the response to acute exposure was strong and immediate: Song Sparrows reduced the song rate and the proportion of time spent singing, lowered perch height, and increased concealment. The decline in the amount of song during the few minutes following playback attributable to the acute exposure was 34.6%. We analyze these results in light of theories about how animals adjust risk taking in response to predation danger. Given that the numbers of their predators have risen steadily for the past few decades and affect the level of singing, we consider the implications for trend estimates of songbird populations based on surveys using auditory methods.

The relationships of breeding stage to daytime singing behaviour and song perch height in Bermuda White-eyed Vireos (Vireo griseus bermudianus)

“…Most of the nest predation in our study occurred during the nestling care stage, which is consistent with the predictions of the nesting stage hypothesis (Morton et al 1993, Burhans et al 2002. Given the increased risk of nest predation during nestling care, and the fact that songs can alert predators to nearby nests (Ellison and Ydenberg 2019), it is perhaps not surprising that Bermuda Vireos produced the fewest discrete songs during this time. Similar declines in vocal activity during nestling care, compared to other stages of the nesting cycle, have been documented in species spanning multiple avian familes, including House Wren (Troglodytes aedon , Wilson and Bart 1985), Yellow-throated and Blue-headed Vireo (James 1999), Goldencheeked Warbler (Bolsinger 2000), Chipping Sparrow (Liu and Kroodsma 2007), and Common Reed Bunting (Emberiza schoeniclus , Brunner and Pasinelli, 2010).…”

Sex-dependent risk-taking behaviour towards different predatory stimuli in the collared flycatcher

“…In addition, due to differences in feather colouration (Ekanayake et al, 2015;Møller et al, 2019), conspicuous motions or behaviours (e.g. singing behaviour, Ellison and Ydenberg, 2019), sexes might attract predators in different ways. Considering these potential sex-specific differences, the value of the current brood and the vulnerability against predation can differ between the sexes, which might actually create differences in risk-taking behaviour (Redondo, 1989;Fernández and Llambías, 2013).…”

Migrant semipalmated sandpipers (Calidris pusilla) have over four decades steadily shifted towards safer stopover locations

“…For example, songbirds reduce the amount and volume of singing after hearing a predator (e.g. Ellison & Ydenberg, 2018). This occurs because singing makes a male conspicuous and so more vulnerable to attack.…”