Birds of a feather flock together: Insights into starling murmuration behaviour revealed using citizen science

Abstract

Pre-roost murmuration displays by European starlings Sturnus vulgaris are a spectacular example of collective animal behaviour. To date, empirical research has focussed largely on flock movement and biomechanics whereas research on possible causal mechanisms that affect flock size and murmuration duration has been limited and restricted to a small number of sites. Possible explanations for this behaviour include reducing predation through the dilution, detection or predator confusion effects (the “safer together” hypotheses) or recruiting more birds to create larger (warmer) roosts (the “warmer together” hypothesis). We collected data on size, duration, habitat, temperature and predators from >3,000 murmurations using citizen science. Sightings were submitted from 23 countries but UK records predominated. Murmurations occurred across a range of habitats but there was no association between habitat and size/duration. Size increased significantly from October to early February, followed by a decrease until the end of the season in March (overall mean 30,082 birds; maximum 750,000 birds). Mean duration was 26 minutes (± 44 seconds SEM). Displays were longest at the start/end of the season, probably due to a significant positive relationship with day length. Birds of prey were recorded at 29.6% of murmurations. The presence of predators including harrier Circus, peregrine Falco peregrinus, and sparrowhawk Accipiter nisus was positively correlated with murmuration size (R2 = 0.401) and duration (R2 = 0.258), especially when these species were flying near to, or actively engaging with, starlings. Temperature was negatively correlated with duration but the effect was much weaker than that of day length. When predators were present, murmurations were statistically more likely to end with all birds going down en masse to roost rather than dispersing from the site. Our findings suggest that starling murmurations are primarily an anti-predator adaptation rather than being undertaken to attract larger numbers of individuals to increase roost warmth.

Testing the potential of Twitter mining methods for data acquisition: Evaluating novel opportunities for ecological research in multiple taxa

“…The number of tweets referencing starling murmurations was considerably lower ( N = 135) than the number of records obtained by Goodenough et al. () ( N = 1,066). In contrast to tweets on the other taxa, geographical location was almost always given in murmuration tweets (2014/15 = 90.3%; 2015/16 = 80.8%).…”

“…The main spatial patterns in the large dataset reported in Goodenough et al. () were also present in the Twitter‐derived data. Specifically, key murmuration hotspots (including Blackpool, Aberystwyth, Brighton, the Somerset levels and East Anglia) were identified in both datasets as were the limited sightings in Scotland (probably reflecting a lack of people recording murmurations rather than an absence of the phenomenon).…”

“…The house spider study (Hart et al., ) ran across autumn and winter 2013/14 from 1st August 2013 (day 1) to 28th January 2014 (day 181). The starling murmuration study (Goodenough et al., ) ran across autumn and winter in 2014/15 and 2015/16 covering the period 1st October (day 1) to 31st March (day 183). See above and individual publications for more details.…”

“…The second study assessed geographical patterns, seasonal peaks, daily rhythms and location of spiders (primarily those in the genera Tengenaria and Eratigena ) within houses during the autumn (Hart, Nesbit, & Goodenough, ). The third study examined starling ( Sturnus vulgaris ) murmuration behaviour to assess the effect of predators and temperature (Goodenough et al., ). Here, for each study subject, we compare Twitter‐mined data with published data to determine: (1) whether the research questions in each study could be answered robustly through Twitter mining (i.e.…”

Complex patterns of collective escape in starling flocks under predation

“…That is what we investigate in the present study for the first time for patterns of collective escape displayed by flocks of European starling ( Sturnus vulgaris ) in response to a raptor (Tinbergen 1951; Feare 1984; Carere et al 2009). These patterns are widespread (Goodenough et al 2017), but their function and underlying mechanisms remain debated (Carere et al 2009; Zoratto et al 2010; Procaccini et al 2011). Our study focuses on the following questions: (i) which patterns of collective escape are displayed?…”