Natural Encounters During Winter in SW Florida

January 12, 2015

Nature Notes by Bill Dunson

Although SW FL gets its share of cooler weather with strong northerly winds during periodic cold fronts, there can be warm interludes during which many animals are quite active and even breed. One of my favorite signs of winter is the breeding of the ragged sea hare, a mollusc lacking any external shell. This picture was taken on Dec. 20. Sea hares are hermaphroditic and can act both as male and female in breeding balls or lines, resulting in chains of greenish eggs. The adults die shortly afterward but the planktonic larvae grow rapidly and metamorphose into tiny sea hares in about 3 weeks. The adults are protected by their disruptive coloring and shape and by toxins in part derived from their algal food; the ink they expel in response to disturbance appears also to be toxic and anti-bacterial.

We recently planted a powder puff plant and soon discovered some interesting insect pests on it. These thorn bugs have an amazing shape to protect themselves from predators- they mimic a thorn and stay in groups and can be surprisingly difficult to spot. I have seen them also on wild blackbead plants in considerable numbers. They can damage plants by sucking out sap and by piercing the bark during egg laying. The female on the left has a pointed spine and the male on the right a flattened spine. They are protected by a toxin and the honeydew they secrete can lead to mold formation. So despite being a very beautiful insect they are not something you want to keep around in large numbers!

If you have planted exotic pipevines you will likely find some polydamas butterfly caterpillars on it someday. Although pipevines have a remarkable flower they are usually planted to attract butterflies so the caterpillars are not considered pests when they eat the vine. You may want to manage your herd of caterpillars by moving some elsewhere if the vine is nearing obliteration. Further north a common caterpillar on pipevines would be the pipevine swallowtail, and I have shown an example from Virginia. They are very scarce in our area of Florida perhaps since the native pipevine is quite small. Can you tell the cats apart? Note that the polydamas has a yellow ring behind its head but otherwise they are quite similar as befits their close relationship. Both show a warning coloration which reflects their toxicity due to poisons obtained from their pipevine food.

An interesting observation I made while driving was encountering a large female peninsula cooter turtle crossing the road. The females are often seen in winter when they come up on land to lay their eggs, but this individual allowed me to photograph the top of her head. The pattern there, a central “arrow” with two “hairpins shaped loops just behind is a primary means of distinguishing this species from the red bellied and chicken turtles. But of course turtles pull their head into the shell when threatened so you often cannot see this pattern.

It is common to see white ibis and great egrets in our yard foraging for lizards and insects. But I was surprised to see this little blue heron engaging in yard foraging recently on two occasions. The ability of birds to flourish along with human civilization often depends on their flexibility in adapting to new feeding possibilities. Thus I was pleased to see this little blue learning some new tricks which will likely improve its reproductive success. I think it may have adopted this terrestrial foraging mode in yards from accompanying white ibis flocks and observing their habits. Such mixed species feeding aggregations of wading birds are common in aquatic habitats but less so on land. So watch for this behavior in your area and see what patterns are occurring.

Another example in our yard of the attraction that a water drip/bath has on birds is this photo of an “odd couple” sharing one of our three baths. A male cardinal and a yellow throated warbler seem quite happy to splash together and enjoy the soaking. They are both regular visitors to our baths and I am happy to see them being willing to share the bath, which some species such as mockingbirds are not.

While standing on our dock I noticed the usual ospreys and sea birds in flight, but the sudden appearance of this eagle sent the ospreys into a rage. There is no love lost between these species since the eagle often steals fish from the ospreys. This was an interesting bird since it is about six months shy of being a full adult. Bald eagles pass through a series of four major plumages called basic 1 to 4. So this bird has a yellow bill, a “dirty” head and tail, a black tail line, is still molting some feathers, and is thus a basic 4+. It is fun to try to age the eagles you see by fitting them into one of the four plumage categories.

The common moorhen or gallinule has been a widespread Florida bird for many years but seems to be declining due to competition for food with the introduced African tilapia fish. At Wildflower Preserve there have been breeding moorhens in some of ponds with the most nutrients and duckweed, but the lack of cover around the edges is a limitation of the habitat. So when floating islands were introduced into one pond it was exciting to see that the moorhens used them for breeding (those with growing plants in them) and just for hanging out on this island that has fewer plants. The original purpose of these plant islands was to remove excess nutrients from the water but the unanticipated benefit to moorhens and other animals has far exceeded the original purpose.

The yellow crowned night heron is the common inhabitant of the mangrove fringe in our yard and we often see them resting or foraging for crabs. They are the characteristic mangrove wading bird in higher salinity waters whereas the black crowned night heron is found primarily in low salinity areas. One of the main differences between them in addition to the colors of the adults is the size and color of the beak. This photo shows how the yellow crowned has a very strong beak, the better to crack crabs, and it is all dark colored. The black crowned has a narrower beak which is usually partly light colored.

So enjoy nature wherever you find yourself in winter, but if you are in Florida you may expect a wide variety of animal activities to continue, alternating with the strong seasonal shifts in temperature due to frequent cold fronts that pass over the state.

Bill Dunson

About Bill Dunson

Bill Dunson, born in rural Georgia, skipped 12th grade and went directly to Yale. Bill subsequent-ly received a PhD in Zoology from the University of Michigan, studying softshell turtles. Bill is Professor Emeritus of Pennsylvania State University thanks to a career spent entirely at that institution, teaching and doing research on the physio-logical ecology and ecotoxiciology of reptiles, amphibians and fish. Always curious about nature, Bill has dedicated his life to learning and sharing his knowledge with others. He has served on many advisory boards here in Southwest Florida to preserve the water that gives life to our region.

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