Abstract
Dear Sheldon:
I found the thesis in the article, The Long Bill of the Toucan, by Roger Williams and Elaine Radford, which appeared in the Feb/Mar '85 Watchbird interesting but not very plausible, when they suggested the large bills evolved as cooling devices.
Although several theories have been proposed to explain the evolution of disproportionally large bills of Ramphastids, cooling is one that has eluded my scrutiny of the literature until now. If, as Williams and Radford state, there is a corrollary between large beak size and hot environment, why is it that the largest beaked birds of the genus Ramphastos may be found at the same low elevations and latitudes as the smallest beaked birds of the genus Selenidera.
Williams and Radford make the assumption that the shorter billed toucanets inhabit the mountains, which is true only of the green toucanets of the genus Aulacorhynchus and these rarely exceed 6,000' elevation - a not very cool environment in the tropics. The Selenidera toucanets, whose beaks are the very smallest (half the length of the green toucanets), live in lowland forests alongside Red Bills, Keel Bills, etc. Keel Bills, incidently, have been recorded as high as 5,000' elevation.
The authors cite Van Tyne's "The Life History of the Toucan" to argue against (who's arguing in favor?) the proposition that bills evolved as protective coloration, a theory that appeared in 1909 and 1910. Van Tyne did not rule it out completely, but stated it was only of slight importance, thus putting it to rest.
He also mentioned other theories, popular in his day (repeated by Williams and Radford), and went on to suggest there may not be any adaptive significance to the great size of these beaks.
Van Tyne's Life History, quoted by the authors, was based on personal field studies conducted over three seasons from 1925-27 and published as his doctoral dissertation by the University of Michigan in 1929. Needless to say, an incredible increase in our knowledge of toucans and evolutionary adaptation has occured in the ensuing fifty-plus years.
Finally, the authors state that the toucan's bill is " ... a light porous structure rich in blood vessels, internally similar to other softbills," suggesting this structure serves as a heat exchanger. I would agree the bills are light and porous, but they are not rich in blood vessels once the bird is mature and the beak has stopped growing. A broken beak on a mature bird does not bleed.
Current consensus holds that beak length and color has something to do with display during courtship, although the size does serve other non-cooling functions mentioned by the authors. Cooling is an interesting idea, but not one supported in the literature.
Sincerely yours, Jerry Jennings~
Dear Sheldon, r
I was quite interested to read the recent article (Dec. 84 - Jan. 85) in the Vet's Corner entitled "The Veterinarian and the Import and Sales of Pet Birds" by Ors. Rosskopf and Woerpel. The article was factual in most respects, as far as I can determine since a paper that I recently presented at the Association of Avian Veterinarians convention in Toronto was the only mentioned reference. There was however, one statement that was referenced to my paper which it did not contain. On page 12 it is stated that "an average of 24 % deaths are to be expected in the quarantine stations." This statement was not contained in my paper and is not true. If it were, importers definitely could not sustain such losses and remain in business.
I will demonstrate how this error could easily be made, and often is. The following statistics were reported in my paper. These were obtained directly from the USDA as official figures for fiscal year 1983.
Received into
quarantine 803,873
Dead on Arrival 40,054 (4.9%)
Died in
quarantine 92,768(12.1% of live
arrivals) Refused entry
(Newcastles) 9,303 (1.15%)
Released from
quarantine 614,782 (76%)
As you well know written papers often are submitted for publication many months before oral presentation of the same material at the meeting. At the time that this data was compiled I had not closely examined these figures but merely reported them as above. I then set out to examine mortality records for 9 quarantine stations with which I worked closely during 1983. I was disturbed by what appears to be a 24% mortality. However, it is obvious upon scrutiny that these numbers are highly inaccurate as demonstrated below.
Dead on arrival 40,054
Died in
quarantine 92,768
Refused entry + ~9-'-,3~0~3 _
Reported dead
or refused 142,126(17.6%)
Received 803,873
Released -614,782(76%)
Dead or
unaccounted for 189,091
Dead or
unaccounted for 189,091
Reported dead
or refused - _14_2-'-,_12"""5 _
Unaccounted for 46,966 (5.8% of
received)
This discrepancy was brought out in great detail in my oral presentation. However, it was not explained in the written paper. I was, of course, very curious as to the fate of the almost 47,000 missing birds and made an inquiry to the USDA. I was told that those figures are inaccurate as they are collected on the last day of the fiscal year, and not limited to stations already released. All birds in quarantine on that day are counted as received but never counted as released. Therefore on October 31, 1983 we can assume that there were 47 ,000 birds in quarantine and that since they are not released in time for development of the annual report, they are missing and presumed dead. Weweremuchluckierin 1982, we only had approximately 25,000 missing and presumed dead. I was assured that the USDA is aware of this problem and will make attempts to correct it for fiscal year 1984.