Featured Articles in This Month’s Animal Behaviour

Having a bath is one of the simple pleasures in life. There are many ways of relaxing in the bath; for children, the fun comes from having a tub that contains more toys thanwater (and the floor contains more water than toys), while for adults, water warms the outside and a good glass of wine warms the soul. For some animals, however, a bath may be a life or death matter; going without a bath might well put them at a greater risk of being eaten. In this month’s issue (pp. 801–807), Ben Brilot and his colleagues, Lucy Asher and Melissa Bateson, show that being able to take a bath before venturing out into the world influences European starlings’ escape behaviour, and that their perception of risk may well be linked to their bathing regime. European starlings are well known for being enthusiastic bathers, and are often seen dipping and splashing in shallow water in the wild (Fig. 1). The current study was inspired by Brilot and his colleagues’ observation that captive birds will often bathe after sessions in which they have been caught and handled, suggesting that bathing may help to repair feathers that been damaged or disordered by handling. Testing this hypothesis is inherently difficult because it involves a kind of Catch-22: to measure whether feather disruption caused by capture and handling is reduced by bathing one needs to catch and handle the birds so causing further feather disruption. To get around this, Brilot and his colleagues cleverly came up with the idea of monitoring the birds’ flight performance. If feather disruption affects flying ability, then birds that are allowed to bathe should perform better than those prevented from bathing. Flight performance was assessed by means of an aerial obstacle course: 38 weighted strings were hung from the ceiling and the birds had to fly through them to reach an ‘escape room’. A loud bang was played as the birds’ cage was opened, to startle them into an escape response, allowing the experimenters to measure their flight speed and the number of strings they hit (a measure of flight accuracy). All the starlings taking part in the experiment were held in aviaries for 3 days, following which they were captured, handled and placed into individual cages. This allowed the experimenters to vary bathing opportunities across different groups of starlings. During the 3-day holding period, one group of birds was given constant access to a water bath while a second group was given only an empty water bath. Following their capture and handling, the birds were given different bathing opportunities. One group was given access to a water bath in the 3 h prior to the test flight, while a second group was again given an empty bath. In this way, the experimenters were able to generate four groups of birds with different bathing experiences: birds that could always bathe, birds that could never bathe, birds that could bathe over the 3 days before the experiment but not immediately before it, and finally, birds that could bathe immediately before the test but had not been able to do so in the 3 days prior to it. This allowed the experimenters to determine not only whether being able to bathe at all had any effect on flight, but also whether it was long-term (3 days) or short-term (3 h) bathing that was most important. Of all these possibilities tested, only short-term bathing had any significant effect on flight speed and accuracy. Birds that had been able to take a bath immediately before testing were more accurate during the test, hitting fewer strings, but they paid for this greater accuracy bymovingmore slowly through the aerial obstacle course. Brilot and his colleagues suggest that these differences may reflect differences in the way that birds perceive risk in the environment. Birds that can bathe may have greater manoeuvrability and hence worry less about escaping as fast as possible, choosing instead to avoid damaging themselves in collisions with the obstacles. Nonbathers, on the other hand, may have perceived a greater threat in their release conditions (both the noise and presence of humans) and therefore chose to escape as fast as possible, weighing the risk of collision as less important than the need to escape. Brilot and his colleagues suggest that the inability to bathe may increase anxiety in captive birds because of their compromised ability to escape from potential danger, and that this anxiety is the proximate mechanism that produces the speed–accuracy trade-off. While Brilot and his colleagues’ experiment cannot demonstrate whether anxiety Figure 1. Taking a bath keeps starlings out of danger. Photo: Jon Hall.