Digital Nature Walk - Tampa

One of my favorite parts of traveling to a new place is exploring how the flora and fauna of that place differ and are similar to what I can find back home. Traveling from the east coast to the west coast, for example, one finds a surprising number of familiar faces, like American robins or dark-eyed juncos, along with local variations on common taxa, like chestnut-sided chickadees and mule deer. Other species, like the American dipper or the bighorn sheep, aren't quite like anything back east. Whether noting a species you've seen a thousand times or adding a new one to your life list, observing plants and animals in an unfamiliar place can spur some really interesting questions about why a species is found in some places and not in others. 

Urban areas have a bit of reputation for disappointing roaming naturalists who are hoping to find something new and exciting on their trip. Just as globalization has diluted local food scenes with McDonalds and KFCs, so it has resulted in a degree of homogenization in urban plant and animal communities. When my brother visited South Africa as an undergrad, he was surprised to find that the birds he saw in the cities there - rock doves and house sparrows - were the same ones that he saw regularly in New Haven. Indeed, these two incredibly successful urban exploiters have been introduced to cities all throughout the world as a result of European colonization and global trade.

Birds like pigeons and sparrows are especially common in many cities for reasons that I will probably discuss in a future post, but for now, it's worth mentioning that a closer look at the flora and fauna of any given city will often reveal some variation, not only in the specific members of these common taxa, but in the community of slightly less common, less immediately visible species that also live there. This variation may not appear in cities closer to home, but it will become very clear if you poke around someplace relatively far away with different environmental conditions.

Last weekend, I went down to Tampa, Florida for a cousin's wedding (a place with very different environmental conditions from New Haven) and, in between all the festivities, I managed to get in a little birding. As one might expect, I saw plenty of common urban birds, such as gulls, crows, and pigeons, but these included some neat local variations on what I would expect to see in Connecticut. I also saw several species that were uniquely Floridian and even added eight new ones to my life list. Below is a brief, ecological summary of the trip.

City Birds:

As I've just alluded to, the most common birds that I saw in Tampa were gulls, crows, and doves. The crows that I saw - mostly fish crows (Corvus ossifragus) with the occasional American crow (Coruvs brachyrhynchos) - were pretty much what I would expect to see in any city along the east coast, but there were some interesting differences in the gull and dove communities compared to what I have seen farther north.

Pretty sure this is a laughing gull - the bill seems too thick and the legs too dark to be a Bonaparte's gull.

The first bird that I saw in the city while looking for someplace to get lunch with some cousins was a laughing gull (Leucophaeus atricilla), swooping between the downtown skyscrapers - or at least, I'm pretty sure that's what it was. There are actually a few American gulls that have a very similar color pattern to the laughing gull, and one of them, the Bonaparte's gull (Chroicoephalus philadelphia), can also be found in Florida. According to my field guide, the main differences between the two are in the size and color of the bill and the color of the feet, but these features were hard to observe in flight. Even when I managed to find a few birds feeding on the ground, I wasn't able to find any birds that lined up exactly with the descriptions I had. Then, on the last night of the trip, I remembered that the colors on range maps actually mean something and discovered that Bonaparte's gulls only show up in Florida during the winter, while laughing gulls are year-round residents - I love when it works out like that! After figuring this out, I looked up the range maps of two other common urban gulls - the ring-billed gull (Larus delawarensis) and the herring gull (Larus argentatus) - that I hadn't seen at all. It turns out that both are found in Florida, but only during the winter, which explains why I was only seeing laughing gulls. 

As is the case with most cities at this point, I also saw plenty of rock doves (Columba livia) in Tampa. Just as, if not more common, however, was another species of pigeon - the Eurasian collared dove (Streptopelia decaocto). Native to subtropical Asia, these lovely doves are known for their ability to quickly colonize new places, especially those made suitable by human modification. During the nineteenth century, they colonized much of Europe and, starting in the 1970s, a population descended from birds released in the Bahamas and on the Island of Guadlupe colonized Florida. From there, they swept across the United States as far north as Washington state. Collared doves are found mostly in urban and suburban areas, as well as low-intensity farmland, and subsequent studies of their dispersal through North American have found that development, warm temperatures, and a lack of forest cover are the best predictors of where they can be found (Scheidt and Hurlbert 2014). These latter two factors are probably why they cannot be found here in New England. 

Female boat-tailed grackle

In addition to these more common urban birds, there were also a few species that were a bit more unique to the southeast. Boat-tail grackles (Quiscalus major) showed up a lot in parks and near water ways and I was surprised to find mockingbirds (Mimus polyglottos) almost everywhere I went. I have seen mockingbirds in residential neighborhoods and strip malls back home, but rarely have I seen them in city centers like I did in Tampa. In general, mockingbirds seem to get more and more common the farther south you go. The urban ones in Tampa at least seem to prefer perching on telephone wires and in treetops rather than on buildings, like crows, pigeons, and gulls will often do. 

Water Birds:

Tampa is located at the mouth of the Hillsborough River, where it meets the Gulf of Mexico. The river flows right through downtown, and the area has a surprisingly diverse community of waterbirds, including several Gulf Coast endemics. The Tampa Riverwalk provides some really great opportunities for bird watching and was right near our hotel, so most of the birds I was hoping to see were wading birds and waterfowl.

Hopefully a mottled duck with chicks

One species I was especially excited about seeing was the mottled duck (Anas fulvigula), a dabbling duck that is closely related to mallards (Anas platyrhynchos) and American black ducks (Anas rubripes). The three species look remarkably alike and, together with the Mexican duck (Anas diazi) represent, depending on one's mood, either a fun or incredibly frustrating challenge to identify where their ranges overlap. Luckily, the individual that I came across in a riverside park was a female with chicks, and since mottled ducks are the only dabbling ducks that consistently breed in Florida, I was able to get a little extra confidence in my ID. Or, that is, until I read about a population of feral mallards that also seem to breed in Florida. I'm pretty sure that this was not a mallard given the color of the bill, but I'm not 100%. Still, I think I'm actually okay with a little uncertainty here, since it was the similarities between the mottled duck and its relatives that drew me to it in the first place. How is it, I wonder, that these species diverged from each other in spite of their similarities and overlapping ranges? In one paper I found (McCracken et al. 2001), the authors examined the mitochondrial DNA of mottled ducks, Mexican ducks, black ducks, and mallards, and found that mottled ducks are much more closely related to Mexican and black ducks than mallards. They suggested mallards first evolved in Eurasia and only colonized the Americas later, after the ancestors of the black duck had been there for some time. Unlike black ducks, neither mottled ducks, nor Mexican ducks migrate, so this may be an explanation for how these two species ended up slitting off - in the warmth of the subtropics, a few populations of black ducks stopped migrating and eventually diverged into their own species. 

Snowy Egret (I'm actually confident in this one)

Aside from the (possible) mottled duck, most of the water birds that I saw along the river walk were part of Flordia's diverse community of herons and egrets. In another fun case of ID confusions, my cousin and I saw six, medium-sized herons flying over the river one evening, five of which were dark in color and one of which was white. This description fits either a flock of six adult reddish egrets (Egretta rufescens), including one white morph adult, or a flock of five adult little blue herons (Egretta caerulea) and one juvenile. I can't really say for sure which it is, but I suspect they were reddish egrets just because they seem (from what I've read) to be slightly more likely to be flying in a group. We also saw a couple of snowy egrets (Egretta thula), hunting on the side of the river and in the surf of the ocean, and a cattle egret (Bubulcus ibis) forging on an island in the middle of the road. Cattle egrets are really interesting birds because they actually evolved in Africa, but seem to have naturally colonized the Americas starting in the 1870s, when a group living on the African west coast made their way across the Atlantic riding the trade winds. They have since spread across much of North and South America, seemingly helped along by the spread of rangeland in the later 19th and early 20th centuries. Unlike other herons, cattle egrets typically hunt on land and, as their name suggests, they can often be seen feeding on insects kicked up by livestock. They are very opportunistic feeders, however, and have found ways to succeed in a number of habitats, including urban ones.

Yellow-crowned night heron

Speaking of successful urban herons, I finally saw my very first night heron while eating dinner with some family near Ben T. Davis Beach. In Chicago, the black-crowned night heron is a well-known member of the urban bird community. Yellow-crowned night herons (Nyctanassa violacea) - the species that I saw - are a bit more secretive, but also seem at least somewhat willing to live near people. They are specialized hunters of crustaceans, especially crabs and crayfish, and can be seen forging both night and day.

Other Animals:

Brown anole

I didn't want to make natural history the main focus of this trip (for obvious reasons) and so I tried to limit the time I spent on it and to focus mainly on birds. Still, Florida is Florida, and stumbling on interesting animals in kind of unavoidable. This is especially true with lizards and, sure enough, while walking back to our hotel the day after the wedding, my brother pointed out a small, brown anole (Anolis sagrei) sitting at the edge of the sidewalk near a planting. Brown anoles are originally from Cuba and the Bahamas, but have been introduced throughout the southeastern United States, where they are now quite common. Anoles tend to do pretty well in urban areas, and urban populations of the Puerto Rican crested anole (Anolis cristatellus) even appear to be evolving longer legs and stickier toe pads in order to better traverse the surfaces found in city habitats (Winchell et al. 2016). Brown anoles in Miami, meanwhile, are slightly larger than those in more rural populations (for reasons that remain unknown) and have more significant parasite loads, but have not developed a higher body temperature preference, despite the greater temperatures found in urban areas (Thawley et al. 2019).

Sources:

McCracken, K. G., Johnson, W. P., & Sheldon, F. H. (2001). Molecular population genetics, phylogeography, and conservation biology of the mottled duck (Anas fulvigula). Conservation genetics, 2, 87-102.

Peterson, R. T. (2020). Peterson field guide to birds of eastern and central North America (7th edition). Houghton Mifflin Harcourt.

Scheidt, S. N., & Hurlbert, A. H. (2014). Range expansion and population dynamics of an invasive species: The eurasian collared-dove (Streptopelia decaocto). PloS one, 9(10), e111510.

Thawley, C. J., Moniz, H. A., Merritt, A. J., Battles, A. C., Michaelides, S. N., & Kolbe, J. J. (2019). Urbanization affects body size and parasitism but not thermal preferences in Anolis lizards. Journal of Urban Ecology, 5(1), juy031.

Winchell, K. M., Reynolds, R. G., Prado-Irwin, S. R., Puente-Rolon, A. R., & Revell, L. J. (2016). Phenotypic shifts in urban areas in the tropical lizard Anolis cristatellus. Evolution, 70(5), 1009-1022.