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Posted by Bryant on 16:36:25 07/01/09
In Reply to: Re: Smooth-billed Anis posted by Roger Hammer
Here is an updated version of a something I posted a couple of years ago about Smooth-billed Anis.
HISTORY
My memory of Smooth-billed Anis in southeast Florida goes back to the mid sixties when numbers of several hundred were regular on the Ft. Lauderdale Christmas Bird Counts and my area in Davie usually reported well over one hundred. Looking back, I believe there was some over reporting of numbers because the Anis moved in noisy flocks of one to three dozen and a party probably encountered the same flocks more than once in different locations. Flocks probably crossed area boundaries and were also counted by more than one party. Despite this, there were certainly a lot more Smooth-billed Anis in Broward County then. In the mid sixties, the Davie area was a mosaic of cattle and horse pastures, orange groves, fencerows, overgrown canal banks, and low-density residential areas.
According to Howell Smooth-billed Anis were only seen sporadically in south Florida before the late nineteen thirties when they were discovered nesting in the Miami area. In the mid forties, they became established in larger numbers south of Lake Okeechobee and spread throughout southeast Florida through the sixties. Since then their population has declined steadily to levels more like those in the nineteen thirties.
The middle of the last century when the Smooth-billed Ani population was increasing in south Florida was a period of massive environmental change. The Everglades were being drained, opening up large areas to farming, ranching, and citrus production, which probably created conditions suitable for Anis. Over the last few decades, these agricultural areas, especially those near the east coast, have been replaced by residential and commercial development isolating pockets of undeveloped and agricultural land, which are rapidly disappearing. Ani populations have plummeted along with other once abundant species such as Carolina Wren and White-eyed Vireo.
When the Smooth-billed Ani population was thriving, they were usually seen in flocks of a dozen or more, there are no flocks known to me today that approach that size. They are communal nesters and the adults share the work of feeding the young, which according to Howell have enormous appetites. It may require the effort of many adult birds to ensure the survival of a few nestlings. The pattern of their decline has been a decrease in flock size with a few adult birds and few if any immature birds followed by their disappearance from the area. The only reliable flock is the one south of Ft. Lauderdale International Airport, which only appears to contain four or five birds. Small groups are occasionally seen near golf courses, pastures, along the edge of the Everglades and in area south of Lake Okeechobee.
Due to the loss and degradation of suitable habitat, it seems unlikely that the Smooth-billed Ani population will rebound in south Florida. While the recent active hurricane seasons disrupted the airport Anis for a while, unusually cold winters probably have more long-term effect on their numbers. This may have something to do with why they have not continued to thrive in the colder areas south of Lake Okeechobee. A few Anis appear to wander in from Cuba and the Bahamas each year so they probably will not disappear entirely but they will be much harder to find.
LACK OF ENDANGERED STATUS
A possible reason for the government s lack of concern about the possible demise of Smooth-billed Anis as a breeding bird in North America is that it was not a part of the nation s avifauna at the time of European settlement. There are plants found in south Florida that are rare and local here but are common in the Bahamas that do not qualify for inclusion as threatened or endangered species because they are considered Caribbean Waifs . It seems that in the eyes of the government Smooth-billed Anis fall into this category.
PRESERVATION?
It is hard to picture a practical plan to save the anis; the era that they were thriving was one of disastrous environmental change in southeast Florida. Massive drainage projects were underway leading to the collapse of the wading bird populations as well as the near extirpation of the Snail Kite. The night sky during the dry season west of my childhood home in Davie was orange from the glades fires and muck fires burned underground for years. In the Everglades Agricultural District poor soil management practices were causing rapid loss of the muck layer due to oxidation, massive areas of former everglades were being converted to Sugar Cane production, and DDT and Parathion were commonly used agricultural insecticides. In this chaos the anis somehow thrived; how do you restore chaos?
The causes for rise and fall of the south Florida Smooth-billed Ani will probably never be known for certain. Sporadic sightings along the coast and in the keys of anis apparently wandering in from the Cuba and the Bahama Islands occurred long before a breeding population became established has and will likely continue. Their establishment as a breeding bird during the middle of the last century was likely aided by changes brought on by coastal agricultural and residential development and massive drainage and agricultural projects in the northern everglades. This period was also one of high hurricane activity in south Florida. Their habit of flying low may lead to high highway mortality and the increase in the number of Cooper s Hawks over the last few decades may also have contributed to their decline.
INLAND DECLINE
Here are some musings about possible reasons Smooth-billed Ani populations have failed in the inland area where there appears to be plenty of good habitat but have held on along the southeast coast in the face of massive habitat loss.
Smooth-billed Anis do not appeared to be directly harmed be temperatures into the mid twenties but their primary food supply of large insects, spiders, and lizards may be reduced. Drainage of the northern everglades has lowered the average winter low temperatures in this area over the last few decades and may have had an adverse effect on the Ani population in this area.
Genetics may also provide a clue to the decline of the inland Ani population and a possible explanation as to why they have disappeared from the southwest Florida coast. The breeding population most likely originated from a small group of birds and subsequent generations were likely subject to the harmful effects of inbreeding. The population on the southeast coast probably benefited from the occasional arrival of new birds from the Caribbean and was able to hold on in the face of ongoing habitat fragmentation, degradation, and disappearance. The inland and southwest coastal populations probably received much less infusion of new blood, which may have contributed to their more rapid decline.
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