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Birds are Far From Boring
Part One: Smooth-Billed Ani
At first look, one wouldn’t imagine the complex lifestyle that these birds lead. Perky and a sleek, lustrous black, the Smooth Billed Ani is not much larger than a grackle. Sporting a long, rounded off tail, the most prominent feature is the beak. The upper mandible curves down from the very top of the forehead as if an extension of the head, which it nearly overcomes in size.
Walking through the thick grasses and scrub forests in southwestern Puerto Rico, you would first tune in to their call, a high-pitched, questioning cry. A couple of the birds you didn’t even know were there would fly out of the grass. Three more would peek out of a scrubby bush to see what was going on while five more would sporadically lift off from the grass and join the others in a nearby tree. Hopping between the branches, they would stare at you.
Anis are very social birds, they move in territorial groups. In Puerto Rico’s Cabo Rojo National Wildlife Refuge, the groups boarder one another, as it is prime Ani habitat. The groups range between one to more than six pairs. Particularly unique is that every female within the group will lay her egg in a nest shared by all the pairs. This can result in as many as 30+ eggs in a single nest!
Species that form social groups primarily benefit from greater protection from predators. One member in a group of foraging anis will remain on a high perch and serve as a “lookout” while the rest of the birds feed. This allows the birds to focus on searching for and locating food without constantly having to watch their surroundings. What perplexes researchers is that these birds work together, to protect the group, but in contradiction to this they compete in the act of bearing young.
As females become gravid, or ready to lay their eggs, they will go to the nest and, before laying, they may push other females’ eggs out of the nest. Sometimes they might even use leaves to cover all the eggs thus-far laid and lay their own egg in the newly formed layer. These strategies of competition allows for a better guarantee that the female and her mate will pass on their genes in the formation of the next generation. This may seem in contradiction to the sociality of these birds, that living in a social group provides better protection than if the birds lived solitarily. Nevertheless, the benefit of single birds within the social group would be that they are less likely to be preyed upon and therefore live to reproduce and, once in the act of egg laying, will further the chances of passing on genes.
In nest monitoring of these interesting creatures, there have been documented instances in which that layer upon layer has been built by one female to prevent another female from passing on her genes. As many as 6 or more layers have been observed. The eggs that are buried do not receive adequate heat due to distancing from the brooding (where a bird sits on the eggs) adult. These eggs are unable to proceed in development and fail to survive.
Furthermore, in the observation of nesting anis, eggs within the nest can be seen to have had failed attempts at their extraction. Ani eggs are bright blue under a thin, calcified layer. When a female tries to push an egg out of the nest, scratch marks from both her toenails and beak are left as blue lines prominently displayed on a white egg. What is interesting is that observing researchers are given a look into which eggs were primarily targeted to be extracted from the nest, as it will bear more scratches than the other eggs. This leads to the question, does the female have an idea of whose egg she is attempting to discard? Additionally, if she is about to lay a second egg, how is she able to discern her own previous egg so as not to throw it out?
Anis can be fairly aggressive when territorial groups come across one another. If both groups happen to be present at the border between them at the same time, havoc can break loose. The birds are highly defensive of their territory and will give chase and engage in violent physical scuffles. Sometimes the more dominant group will cause the lesser to abandon their territory and the victorious will take over the area. Another observed interaction, this exceedingly rare, was the attack of one group on the nest of another. During the day when the birds are away from the nest to forage, individuals from another territory approach the nest and peck open eggs, destroying them. In Cabo Rojo the observation was of a multi-day attack, one egg at a time. The actual act was not observed, only the resulting damage.
In conclusion, it cannot be denied that this species of bird is enormously fascinating with it’s variety of unique behaviors. While, overall, not particularly rare or threatened, it might take a birding vacation in order for readers to observe the Smooth-billed Ani in nature. Their only population in the U.S. is the southern tip of Florida which has been declining rapidly. The thought is that more common frosts in the area is a possible cause. Much more robust populations occur across parts of Central America and, more extensively, South America. Latin American Anis have fared well in the age human development, as they thrive in farmed areas. They favor expanses of open grass where they can easily find their main sources of food, grasshoppers and other insects as well as small lizards. If you’re a birder, or even if not, you will be drawn to these birds. They are easily observed in the wild and, with their spunky character and remarkable behavior, it wouldn’t be trip wasted!