William E. Davis, Jr.
From an oceanside rental home on Long Beach Drive, Big Pine Key, Florida, I observed White Ibises (Eudocimus albus) bathing on seven days during March and April 2020. In all but one instance the bathing involved more than one bird. The first bathing observations were on March 4. I was watching a flock of 14 White Ibises forage in the beach wrack in our backyard. At about 6 pm, a few of the ibises walked into an adjacent tidal pool and began to bathe. The bathing event began with a bird immersing its head (Figure 1), then lowering its body into the water, soaking its wing and body feathers, and shaking its wings and tail feathers (Figure 2), then shaking all of its body feathers (Figure 3). After several minutes of this bathing behavior, the first bird walked out of the pool and began to preen. As birds emerged from the pool, others went into the pool and bathed (Figure 4) until all of the Ibises were out of the water and preening. At about 6:15 pm, all of the ibises took flight together and left.
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Fig. 1. Bathing generally started with the bird immersing its head.
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Fig. 2. The bird partly submerged and beat its partially open wings.
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Fig. 3. The bird shook its body feathers.
On March 21 at 12:40 pm, in a group of four ibises, one bird began to bathe and continued to do so for about 10 minutes. It stood in shallow water and ducked its head with its body half submerged. It fluffed its body feathers and vigorously flapped its wings. It stood and fluffed, usually with the wings extended. On four occasions following extensive bathing, the ibis raised its wings and flew a few inches to a foot in the air. This probably aids in drying the bird and settling its feathers. Each bout of bathing was followed by extensive preening and sometimes chin-scratching.
On March 23 shortly after 4:30 pm, five ibises flew in and lit in shallow water near a clump of dead mangroves. They stayed together as a group, and 10 minutes later I noticed that they were bathing. They were joined by two more ibises in the bathing activities. Every minute or so, the bathing ibises were joined by one or more ibises until, by 4:55 pm, a total of 14 ibises had bathed. One by one, the original five ibises flew up into the nearby mangrove and preened. Extensive preening often occurred between bouts of bathing. After preening, the ibises flew inland one by one. At 5:10, when I ceased observation, there were still five ibises preening in the mangrove.
On March 24 at 3:25 pm, I noticed two White Ibises bathing in the same pool in which bathing had occurred the previous day. A third ibis came in and bathed. The following afternoon, March 25, at 3:40 pm, three ibises began to bathe near a mangrove inshore from the site used during the previous two days. After a few minutes the three birds, one at a time, flew over to a mangrove. All three preened extensively. Two of the birds opened their wings repeatedly, and in one instance one preened its side feathers under the wing. One bird was observed scratching under its chin. An additional six ibises bathed before I discontinued observations.
At 4:55 pm on March 26, a single White Ibis began bathing in a pool near the mangroves. As is always the case between these cleaning bouts, it preened and, on several occasions, scratched its chin. It also rubbed the upper part of its back with the back of its head. At 5:02 pm, a Willet (Tringa semipalmata) approached the bathing ibis and began bathing, too. The power of suggestion in birds to join a bathing bird seems remarkable. A second ibis joined the ibis and Willet. A total of seven ibises, including an immature bird, bathed and all flew to a dead mangrove to preen.
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Fig. 4. After bathing, the ibises walked out of the pool and stood preening.
On 14 April, at 6:00 pm, I noticed that two White Ibises were bathing out by the flats, putting their heads under water, bringing them up and then flapping furiously on the water. A third ibis joined the first two, and soon one of the original two flew off to the exposed flats and began to fluff and preen. Preening is apparently an important aspect of bathing. Occasionally they would raise their wings. I watched a total of seven ibises bathe and preen out on the flats. At one point a Great Egret (Ardea alba) walked over and preened with the ibises. This is another example of the compelling attraction involved in group bathing and subsequent preening in birds.
The Birds of the World's (formerly Birds of North America) White Ibis account (Heath et al. 2020) briefly describes ibis bathing and mentions that "group bathing is common during courtship at the edges of colonies." They provided no additional references to, or comments on, bathing behavior. The bathing ibises were not near any active breeding colony and were not showing any signs of courtship behavior, although they did have the bright red faces associated with breeding season; they appeared to be simply foraging together. I suspect that this group bathing behavior extends beyond breeding season and may occur throughout the year.
The timing of group bathing may be influenced by tide and time of day. The ebbing of the tide influences the depth of water on the somewhat irregular substrate surface, forming shallow pools. Bathing is usually within several hours of low tide. However, on March 4, the time differential was more than six hours. More data will be required to assess the influence of tide on the timing of bathing. All but one of the observations of ibises bathing began late in the day between 3:20 pm and 4:45 pm.
Group bathing by White Ibises appears to be flexible but follows a general pattern. A group bathing event begins with one or a few birds and apparently draws in ibises that can see the bathing event occurring. Group bathing is not unique to White Ibises. Many species of shorebirds also bathe in groups (Davis 2016).
Literature cited
- Davis, W. E. Jr. 2016. Shorebird Behavior on their Wintering Grounds. Bird Observer 44: (4) 266-69.
- Heath, J. A., P. C. Frederick, J. A. Kushlan, and K. L. Bildstein. 2020. White Ibis (Eudocimus albus), version 1.0. In Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, New York. https://doi.org/10.2173/bow.whiibi.01