In a WhatsApp local list, Tyler Stuart asked about causes of apparent recent Limpkin vagrancy further abroad than the species has been known to wander. So, I tried to do some reading to see what I could find out.
-- Limpkins are apparently very little studied and not much is truly is known about them. The few studies that have occurred have apparently been only on the Florida population. So while almost every source says they eat apple snails almost exclusively, I do wonder if other populations were studied they would still find such high reliance on apple snails. They seem to prefer the snails and other mussels, but as we have seen in the Colorado visitor, they also can eat earthworms, etc. They are not known to breed in places where apple snails don't exist, however, according to Birds of the World - at least so far.
Around the end of the 1800s/early 1900s, Limpkin populations were greatly reduced by hunting and loss of habitat due to swamp-draining by humans for development. Loss of habitat is still a concern in Florida, but the population rebounded from earlier lows, but since is still facing general slow decline due to loss of habitat. There have been no formal population studies on Limpkin population numbers so they are not actually well understood, but some information is inferred from CBCs, etc. In spite of pressures from humans, they are noted as being particularly tolerant of human presence even at/near nests.
Evidence from digs/studies at old Native American sites shows that the current Limpkin range is reduced and that it once was breeding and in larger population in Georgia, and possibly Mississippi and south Texas. They are beginning to expand breeding range into southern Louisiana, following invasion of apple snail there. The south Texas birds appear to have been more likely to be the Caribbean subspecies instead of the Florida one (our CO bird seems to be the Florida (speckled) variety).
Limpkins are not known as migrators and often tend to stay where they are born, but there are obviously some that do wander from natal grounds. It speculated that birds may occasionally wander due to drought or food competition and go wherever rain/habitat allows, but there have been no studies.
Limpkin Vagrancy in the United States and up to Nova Scotia is on the upswing from first being noted in the 1950s. The timing of that, however, seems to coincide with the recovery of the species from the earlier population plummet, and their prior range and behaviors are not very well known but instead are inferred from archaeology and a handful of written records. We also do not seem to have a lot of information about the subspecies that typically reside outside of the United States. Most people believe Limpkins will continue to increase vagrancy wherever habitat/food allows but people have only speculated at reasons such as climate change, habitat loss, recovery from historical losses, etc.,
I wonder if Limpkin vagrancy could be a ripe topic for an ornithology thesis project.
Similarly, Hepatic Tanagers are another species of note here recently in COBIRDS that seem particularly ripe for study. Birds of the World notes that almost nothing is known - "notably reproduction, diet, and population biology [are unknown]. Such basic information as quantitative habitat information, vocal repertoire, incubation period, renesting, and a description of the natal down is lacking, so this species offers much potential for a study of life history."
Hepatic Tanagers are believed to have expanded range in the United States in recent years, which may be a factor in Colorado occurrences - but no one knows why and it has not been studied- a similar story to the Limpkin vagrancy.
Diana Beatty
El Paso County
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