BirdWalk Newsletter

Transcription

1 BirdWalk Newsletter Magnolia Plantation and Gardens Walks Conducted by Perry Nugent Newsletter written by Jayne J. Matney Cover Photo Angie Bridges Mississippi Kite How do birds tolerate the harshest of weather? The newsletter has already addressed what birds do during storms (see newsletter ), so this time the emphasis will be on extreme temperatures. First, birds are warm-blooded, or endothermic, which means that they can maintain a nearly constant body temperature despite the outdoor temperatures. Therefore, their bodies, just like ours, are conducting thermoregulation on a constant basis by way of natural processes from within their bodies. Unlike humans, they do not sweat, but they

2 do have other ways, both physiologically/anatomically and behaviorally to withstand severe temperatures when faced with them. Warm-blooded animals have different ranges of body temperatures. Birds body temperatures vary by exact measurement and by times of the day, but the average body temperature for birds is approximately 105 degrees Fahrenheit or 40 degrees Celsius. The severity of the temperature outside and the size of the bird are factors which can influence survival rates. The smaller birds, like the Common Yellowthroat pictured on the left, have a distinct disadvantage due to having a smaller body core to help them maintain body temperature. The good news is that the ability to maintain fairly constant body temperatures enables birds to inhabit many varieties of terrain around the globe. So how exactly do birds survive extreme temperatures? Looking at the non-feathered parts of the bird s body, basically the legs, feet, and beak, there Photo by Guenter Weber are ways birds stay cool or warm. Scales are found along the legs and feet that can be tough armor for protection against extreme conditions such as temperatures. Speaking of legs, some birds such as the vultures will use urohydrosis to keep cool in hot conditions. This is where the bird will urinate down the legs to help cool them off. The evaporation process of the urine will give a cooling effect for the bird. The legs can maintain constant temperatures internally as well by the counter currents of the warm and cool blood vessels known as veins and arteries. This enables a retention of heat within the legs and feet during cold conditions by not allowing that heat to be released too readily. Most birds can also regulate blood flow during cold conditions to further hold in body heat. Ehrlich, Dobkin, and Wheye from Stanford also state that while a core temperature of a duck or gull standing on ice may be 104 degrees F, its feet may be only slightly above freezing. The beaks stay cool or warm up according to the blood flow regulation within this body part. When the blood vessels open up or dilate, more warmth from

3 the body core can get to the beak and that heat can get released during warm conditions. When blood vessels constrict, the beak can have a more warming effect for the body core due to lack of body heat being release out of the beak during cold temperatures. With the rise and fall of environmental conditions, the birds can adjust their metabolic rate to heat up the body (increasing metabolic rate), or cool down (decreasing metabolic rate). Expenditure of energy is necessary when the rates go up. When birds are under stress because of lack of food for energy expenditure or if the bird is under duress due to cold weather conditions, they are able to slow down their metabolism and go into regulated hypothermia or torpor. Their metabolism, and therefore, their body temperature goes down with the conditions around them. In an Article for Stanford, Ehrlich, Dobkin, and Wheye, explain: Red-tailed Hawks drop their nocturnal body temperature by 5 to 7 degrees below their daytime temperatures. Hummingbirds swifts, and poorwills enter a state of torpor in which body temperature may drop as much as 50 degrees F for several hours during the night or for days during extremely inclement weather (1988). This may seem like a perfect scenario, but it does cost some energy loss when coming out of this torpor state therefore will need immediate sustenance. Also, the bird is unprotected and more vulnerable to predators during this state. A more shallow torpor may be more widespread amongst birds than originally predicted. Like us, birds will shiver as a simple and effective way to warm up the body core during cold weather conditions. This reaction to cold is the muscles working to help warm up the body. Molting is another physiological/anatomical way for the birds to counter the temperatures. They will release feathers in preparation for the hotter months and increase feather coverage during the colder months. The actual coloration of birds are not just viable for protection and mating reasons. The dark feathers can be used to absorb heat in the winter and the lighter feathers can be used to reflect heat in the summer.

4 Posturing by birds is a useful behavioral tool to improve on this aspect of their morphology. This leads us to the behavioral aspects of dealing with extreme temperature conditions for birds. Behavioral thermoregulation can be done many ways. Posturing as mentioned before, is when a bird turns its body toward or away from the sunlight depending on the temperature regulation being made. Anhingas are notorious for posturing in the sunlight with open wings batman pose to regulate body temperatures after being in the water. They will then turn At the plantation, we call this The Batman themselves to take Posturing by an Anhinga Photo by Jo Frkovich advantage of the breezes when they are needed and the direct sunlight when needed. Likewise, birds will turn away from the direct sunlight to reduce exposure to environmental heat or they may position themselves in the shade when they are too hot. Some chicks will take refuge in the shade of their parents. Most people have seen birds protect their legs and feet by tucking one leg and standing on one foot or maybe plopping down on the ground to cover the legs and feet with feathers for a while. Birds will also roost together or huddle like the penguins. Birds have also been seen many times tucking the head and beak into feathers for consolidating body warmth. Others will puff-out their feathers in cold conditions to promote a thicker layer of feathers and warm air from the body as an insulation. Right: A young Great Blue Heron puffing out feathers for insulation Photo by Jo Frkovich

5 Here on the plantation, a visitor or bird watcher may notice the Great Blue Heron slouching the wings down and laying them open. This posture is to help them cool their body core. See picture left: Photo by Jo Frkovich Another behavior which is seen during the hot, summer days is the birds holding their beaks open and tongues out. Opened beak and neck fluttering Photo by Cathy Padgett

6 Many times they will include a fluttering of the throat to go along with the open mouth behavior. This is their way of panting like a dog. We see alligators do this as well in order to release excess body heat. Many soaring birds, such as birds of prey, vultures, and gulls, will fly and soar higher up in the altitudes on a hot day as often as they can for cooling purposes. The temperature in the air decreases fairly rapidly as you increase in altitudes. Bathing is a popular go to method of cooling off on hot days. Birds will walk through, dunk into or twist their feathers around and splash up water onto their bodies. Of course, migration is always an option. Birds will arrange their lives by moving, or migrating, around the globe just to accommodate the ability to survive temperature changes. Barred Owl cooling off with a quick bath! Photo by Guenter Weber There are pro s and con s to some of the things we do to try to help these birds during extreme weather. Sometimes, we believe we are helping when actually we are not doing what is best for them. Of course, keeping the food sources available can be one way to help at these times. When food sources are available, these birds can build fat for insulation during cold weather. They can

7 also have readily available food after coming out of torpor states when reenergizing is necessary. The problems with the feeders can happen when the feeders are placed too close to windows or placed in such a way that makes it easy for predators to feed off of the birds that are feeding off of the feeder. Cats are a primary predator for these feeder birds. It is recommended that you make sure the food you are providing is healthy. Bird baths are a way for people to help, but keep in mind that the predators can be an issue with these as well. Also, the depth of the water is important for certain types of birds. The smaller birds cannot properly utilize a bird bath that is too deep. Mark Kiser, Great Florida Birding and Wildlife Trail coordinator goes further in saying that you can attract birds best with water features that gurgle, rush over rocks, or drip. He also suggests misters or sprayers as the best means for providing water without dealing with water depths, bacterial or algae growth in baths, disease or pathogen contamination, or contributing to mosquito larvae habitat. Cleaning your bird bath once a week and adding ice in the mornings are other suggestions. The easiest way to help is by providing plenty of shade in your yard with vegetation. Trees and use of tiers and bushes can be the best way to do this. Another way to provide shade is through sheltering. Roost boxes, bird houses, and brush piles are safe places for birds to stay out of the elements. Nature has a way of taking care of itself in most conditions. Helping the birds do what they naturally would do is the best way to help without causing unwanted problems. The magic fades too fast The scent of summer never lasts The nights turn hollow and vast But nothing remains..nothing lasts. Sanober Khan Photo right: Yellow-crowned Night Heron Photo by Jo Frkovich

8 Even though the plantation is still getting some days in the 80 s, fall is upon us. October 8 th was an overcast, breezy day. Thirty-three species were seen. There was a gradual increase in Blue-winged Teal and the Wood Duck were in good numbers with 20 individuals. The Pied-billed Grebe, Anhinga, Great Blue Heron, Great Egret, Snowy Egret, Little Blue Heron, and White Ibis were all accounted for. A Yellow-crowned Night Heron was observed along the cross dike and 60 Common Moorhen were viewed in the large impoundment. Laughing Gulls and Turkey Vultures were seen flying overhead. One prey bird, a Redshouldered Hawk, made itself known amongst the trees. Two Red-bellied Woodpecker, one Downy Woodpecker and four Pileated Woodpeckers were also identified. Special sightings were the Prairie Warbler at the high Red-shouldered Hawk in the Fall Photo by Chuck Fuhrman dike and the American Redstart located in various places on the property. The other passerines, or perching birds, were: Mourning Dove, Eastern Phoebe, White-eyed Vireo, Blue Jay, American and Fish Crows, Carolina Chickadee, Carolina Wren, Northern Mockingbird, Common Yellowthroat, Northern Cardinal, Red-winged Blackbird, Common Grackle, and Boattailed Grackle.