Why our survival 
depends on theirs 
Remorseless 
Havoc 
Robert McNally 
Passionate, moving, and 
beautifully written, SO 
REMORSELESS A HAVOC 
thoroughly details the evolu- 
tion, physiology, instincts, 
and migratory patterns of 
whales and dolphins, the lat- 
est theories on the nature of 
their intelligence, and their 
significance in man's art, 
mythology, and literature. 
Illustrated throughout with 
photos, diagrams, and line 
drawings. 
“Undoubtedly one of the 
best books about whales 
and dolphins and their fate 
at human hands that I've 
ever read '.'—Farley Mowat 
“Excellent....! couldn't have 
stopped reading, even if I 
had wanted to.” 
—Roger Caras 
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turn in April and May, a modest de- 
cline in kill numbers in the spring 
would not be surprising, and tallies for 
many species collected at the WCTV 
tower during the years from 1955 to 
1980 conform to this general expecta- 
tion. For example, 353 prairie warblers 
were killed in the spring compared with 
533 killed in the autumn. For many 
species, the disparity between spring 
and fall mortality is more striking, and 
many are grossly overrepresented in 
fall collections. These include the mag- 
nolia warbler (519 of 520 total kills oc- 
curred in the fall), blackbumian 
warbler (374 of 374), chestnut-sided 
warbler (483 of 483), bay-breasted war- 
bler (466 of 466), ovenbird (8 1 1 of 834), 
brown thrasher (277 of 290), veery 
(1,018 of 1,114), song sparrow (271 of 
274), and white-throated sparrow (512 
of 551). A few species, on the other 
hand, have been found more frequently 
in spring than in fall (blackpoll warbler, 
158 versus 5; green heron, 27 versus 7). 
Some of these differences probably 
reflect seasonal differences in routes 
and migration behaviors. The autumn 
route of the blackpoll warbler is largely 
across the open Atlantic Ocean, where 
prevailing winds help carry the birds to 
their winter homes in South America; 
the spring route is primarily through 
the Caribbean and peninsular Florida. 
Many other species, in contrast, pass 
through north Florida in large numbers 
in the fall on their way to Central and 
South America. These species, along 
with those that are winter residents 
near the tower, show up in the autumn 
kills. In the spring, some of the long- 
distance migrants fly to the west of 
WCTV. Other species seldom found in 
the spring kills, such as winter-resident 
sparrows and some migrants that fly at 
night in the fall, are thought to migrate 
northward during daylight hours. 
A few species, most notably cedar 
waxwings and red-winged blackbirds, 
show peak WCTV tower mortality in 
the winter months of December, Janu- 
ary, and February. The cedar wax wing 
is a winter wanderer in northern Flori- 
da, and red-wings maintained a winter 
roost near the tower for many years. 
June is consistently the month of lowest 
WCTV tower mortality. Over the years 
about 42,000 tower kills have been 
counted by the Tall Timbers staff, but 
only 28 individuals died in June. 
Firm conclusions about the relative 
abundances of migrating species cannot 
be drawn on the basis of tower kill re- 
cords alone because many factors affect 
the results. Early fall migrants such as 
Louisiana waterthrushes and orchard 
orioles, for example, are poorly repre- 
sented at the WCTV tower probably 
because of the lower frequency and re- 
duced severity of cold fronts in late July 
and August. A particularly strong front 
coinciding with a major wave of mi- 
grants may also produce potentially 
misleading statistics. On the night of 
October 8, 1955, about 2,000 palm war- 
blers died at WCTV. This kill is the 
largest for a single species ever record- 
ed at WCTV, yet the palm warbler is 
not otherwise particularly abundant in 
fall collections. 
Information from tower kills is most 
valuable when compared and evaluated 
with data from other sources, such as 
those derived from fieldwork. For ex- 
ample, in the southeastern United 
States, yellow-billed cuckoos appear 
much more frequently during spring 
migration than do black-billed cuck- 
oos. This field observation is supported 
by the tower kill results: on the average, 
about twenty yellow-bills are killed per 
year compared with about two black- 
bills. Sometimes, however, the data 
conflict. Tower results argue that the 
peak of yellow-billed cuckoo spring mi- 
gration is the middle of May, much lat- 
er than field observations would 
predict. This apparent contradiction 
has been explained. Some yellow-bills 
do arrive in early April and make them- 
selves known by their distinctive call 
notes. But many more birds, traveling 
at night and formerly unnoticed, con- 
tinue to pass through until late May, 
well after resident cuckoos have fledged 
young. The WCTV study has also in- 
creased our knowledge about the clay- 
colored sparrow, a species seldom 
observed in the field and presumed rare 
in Florida and nearby states. Six speci- 
mens have been recorded at the tower, 
showing that while the species is rare, it 
does pass through the area regularly. 
Tower kills make possible the accu- 
rate determination of the sex and age 
classes of migrants, sometimes with un- 
expected results. At WCTV, female 
ruby-crowned kinglets are significantly 
more abundant than males. Females of 
this species are now believed to winter 
farther south in the United States than 
males. This behavior could have 
evolved in response to selection pres- 
sures favoring early arrival of males on 
choice, northerly breeding grounds in 
spring; it would also lessen intersexual 
competition during the winter. 
Sometimes, the various age classes of 
a given species occupy largely different 
wintering grounds. Many autumn birds 
