A few years ago I asked an ornithologist friend of mine what urban birds such as starlings and house sparrows ate. His answer was that it was probably a mix of bottle caps, cigarette butts, and McDonald’s French fries. I’m only partially satisfied with that answer, and so try to keep an eye on what urban birds eat wherever I go.
Since moving to Miami four years ago, I’ve observed several cases of birds consuming anoles. After watching a Common Grackle feed an anole to a fledgling a few days ago, I thought I’d compile and share these observations with AA readers.
Non – passerines
American Kestrels (Falco sparverius)
Red-shouldered Hawk (Buteo lineatus)
White Ibis (Eudocimus albus)
Great Egret (Ardea alba)
Cattle Egret (Bubulcus ibis)
Loggerhead Shrike (Lanius ludovicianus)
Boat-tailed Grackle (Quiscalus major)
Common Grackle (Quiscalus quiscula)
Many of these birds might be considered expected predators of anoles (esp. Kestrels & Great Egrets), but others are perhaps more notable, given the species of birds involved. The non-passerine predators seem unsurprising. These predators forage conspicuously along open, weedy edges, and highway medians for small vertebrates and invertebrates. For example, I’ve seen a Red-shouldered Hawk pick off a nice male A. sagrei from the landscaping in a Target parking lot. And I’ve seen hundreds of Great Egrets and Cattle Egrets devour brown anoles at a rate that would make the most adept anole catchers swoon. It’s hard to estimate this rate from casual observation, but on a recent visit to Fairchild Botanical Gardens, a particularly bold cattle egret followed me around for about half an hour, during which time it caught and consumed over a dozen Anolis cristatellus and A. sagrei (estimated rate ~ 24 anoles/hour!). There was no outward sign of satiation or fatigue in this particular individual and I’ve heard similar stories from other Fairchild visitors suggesting that egret predation can be a significant source of mortality for urban anoles.
But what I find more interesting are the passerine predators. Among the species I’ve noted here, the shrikes, while common in some areas, don’t seem to be terribly abundant and their importance as anole predators is unclear. However, both species of grackle are terribly abundant in urban and suburban areas of south Florida year-round (parking under a choice roosting tree will convince you). To be clear, I’ve only witnessed two grackle predation events during my tenure in S. Florida, however given their active foraging along side-walks, in backyard gardens, and parking lots (prime habitats for urban anoles), I suspect that the importance of these passerine predators might be easily overlooked. Other passerines such as Blue Jays, crows (American and Fish), and possibly Mockingbirds might also be overlooked predators of anoles, but I just don’t know.
On a final note, to get a photo to accompany this post, I followed the female Boat-tailed Grackle pictured above for about five minutes as she wound her way around, under, and atop Ficus and Bougainvillea hedges in what seemed like an obvious search for anoles. I didn’t see her catch anything, but seemingly annoyed by my shadowing she flew over to a dumpster, disappeared for a moment, and emerged with a French fry.