passing the WCTV tower are trans- 
Gulf migrants about to embark upon a 
nonstop flight to Central America. To 
the east in central peninsular Florida, 
the WDBO tower, also extensively 
monitored, is in the flight path of many 
circum-Gulf migrants: those that will 
fly directly to South America or island 
hop through the West Indies. In a com- 
parison of autumn kills at the WCTV 
and WDBO towers, fourteen species 
were observed to have significantly dif- 
ferent age-class ratios. Out of a total of 
2,410 common yellowthroats, for ex- 
ample, adults constituted 29 percent of 
the kills at WCTV and 64 percent of the 
kills at WDBO. The comparison was 
based on data from two different time 
periods because figures were not avail- 
able for overlapping years, but our ex- 
perience has been that mortality 
patterns do not vary considerably from 
year to year. The evidence suggests, 
then, that the two towers may well be 
sampling different age cohorts of mi- 
grants on their way to separate winter- 
ing areas. 
Whatever the sex or age, almost all 
birds killed at towers are nocturnal mi- 
grants since diurnal migrants easily 
avoid collision with communication 
towers. The food habits of a species ap- 
pear to be important in determining the 
time of migration flights. For songbirds 
that forage on the ground or in wooded 
areas and rely on daylight to find prey, 
migration flights occur primarily at 
night during the normal sleep period. 
Thus these birds avoid what would oth- 
erwise be at least a 36-hour fast (from 
the night preceding a daytime flight 
through the following night). Species 
that normally feed on the wing during 
the day tend to be diurnal migrants, 
simply feeding as they travel. 
Most sparrows, warblers, vireos, 
kinglets, cuckoos, wrens, thrushes (ex- 
cept the eastern bluebird), and mimic 
thrushes are nocturnal migrants, and 
all of these groups are well represented 
in the WCTV morgue. Waterfowl and 
shorebirds, some of which migrate at 
night, are rare at WCTV, but this may 
be partly because the tower is not locat- 
ed on a major flyway. Hawks, swifts, 
and swallows — familiar diurnal mi- 
grants — are represented by a total of 
only fifty-four corpses in twenty-six 
years at WCTV, and some of these 
deaths may have occurred during cre- 
puscular flights. Several of the findings 
have been a surprise. Eastern kingbirds 
and American goldfinches are common 
migrants at Tall Timbers but are rarely 
found among the tower kills. Perhaps 
they migrate primarily during the day. 
And although cardinals in the South- 
east are generally thought to be nonmi- 
gratory, the species is apparently a 
common night migrant at Tall Tim- 
bers, judging by the fifty-four speci- 
mens recovered between 1955 and 
1980. 
The WCTV tower returns suggest 
that species occasionally migrate in 
large flights. On May 2, 1964, 104 gray- 
cheeked thrushes were picked up at the 
base of the tower. This represented well 
over half the total gray-cheek kills re- 
corded in the first eleven years of the 
study. On October 5, 1957, 126 gray 
catbirds were found at the tower. The 
same night brought down 54 summer 
tanagers, 163 American redstarts, 194 
hooded warblers, and about 50 north- 
ern waterthrushes. Seventy-six prairie 
warblers were tallied on August 20, 
1957, and the record kill of about 2,000 
palm warblers in 1955 has already been 
mentioned. 
Red-eyed vireos, by far the most 
abundant of the kills at WCTV and per- 
haps the most common species in all 
tower kills, account for about 17 per- 
cent of total deaths in the Tall Timbers 
study. Average mortality at this tower 
alone is about 286 birds per year, sug- 
gesting that the total slaughter of red- 
eyed vireos at all towers must be 
enormous. In contrast, a number of 
species (including the double-crested 
cormorant, horned grebe, great horned 
owl, and white ibis) have been recorded 
at the tower only once, but undoubted- 
ly the most unusual casualty was a 
black-capped petrel found on Septem- 
ber 11, 1964. This normally oceanic 
bird had apparently flown inland with 
the eye of a hurricane, only to succumb 
to a steel pillar. 
Despite the huge number of speci- 
mens of all sorts collected in this 26- 
year study, only two birds carried 
bands: a brown thrasher, picked up on 
October 19, 1966, and banded on May 
23, 1964, at New Brunswick, New Jer- 
sey; and a veery, picked up on Septem- 
ber 25, 1965, and banded on September 
1, 1965, near Chestertown, Maryland. 
The largest single night kill ever re- 
corded at Tall Timbers occurred just 
one week after the survey was begun. 
On the morning of October 9, 1955, 
Stoddard arrived at the base of the first 
WCTV tower, a 673-foot-tall structure, 
to find the grounds littered with an esti- 
mated 4,000 to 7,000 dead and dying 
birds; only 1,988 specimens of 62 spe- 
cies were identified before the rest were 
lost to decomposition and scavengers. 
In 1960, the original tower was re- 
placed by the present 1,010-footer, with 
twenty-one guy wires, three sets of 
blinking red lights, and twelve small 
nonblinking red lights. The taller tower 
has not increased the recorded number 
of tower kills, and since 1967, recover- 
ies have actually gone down sharply. 
The lower tallies, however, are perhaps 
primarily due to a reduced program of 
scavenger control. 
One of the most dramatic findings of 
the WCTV study concerns the pro- 
found influence of predators and scav- 
engers at the tower. If left unchecked, 
predators harvest large numbers of the 
birds killed and crippled during the 
night and early morning. The problem 
can hardly be overstated. On nights 
when there are massive kills, predators 
become supersaturated with food and 
do not severely influence census counts 
of tower kills, but on more usual migra- 
tion nights, when perhaps five to one 
hundred birds are knocked down, scav- 
engers may cause the disappearance of 
50 to 100 percent of the kills before a tal- 
ly can be made. The Tall Timbers staff 
has conducted many studies to docu- 
ment predator influence on counts. One 
night, for example, sixty experimentally 
marked corpses were scattered about 
the tower; by early morning all had dis- 
appeared. Many specimens vanish with- 
out a trace, but others leave “feather 
puddles” as evidence of the deed. The 
perpetrator may also leave clues to its 
identity — pellets, scats, feathers, tracks, 
scents, or partial prey remains. 
We believe that entire predator- 
scavenger communities may develop 
around productive towers. The WCTV 
ornithologists have had to contend with 
a wide variety of competitors, including 
feral cats and dogs, escaped hogs, opos- 
sums, raccoons, bobcats, foxes, and 
skunks. Two of the more unusual scav- 
engers observed at the tower were a 
toad found trying to swallow a dead 
bird and a cotton rat surprised while 
chewing on a ruby-crowned kinglet. 
Loggerhead shrikes frequently add 
WCTV birds to their larders, impaling 
them on barbed-wire fences at the tow- 
er site, and flocks of crows search the 
grounds each morning. Earwigs, yel- 
low-jacket wasps, and a species of gray 
garden slug, Deroceras laeve, often feed 
on the dead birds. The eight species of 
ants that eat the tower birds, reducing 
them to a pile of feathers and bones in 
just a few hours, can be especially an- 
noying when museum specimens are 
desired because an ant-infested bird 
may at first sight look intact and un- 
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