American Society of Mammalogists

Bats Killed at a North Florida Television Tower: A 25-Year RecordAuthor(s): Robert L. Crawford and W. Wilson BakerReviewed work(s):Source: Journal of Mammalogy, Vol. 62, No. 3 (Aug., 1981), pp. 651-652Published by: American Society of MammalogistsStable URL: http://www.jstor.org/stable/1380421 .Accessed: 04/10/2012 22:17

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GENERAL NOTES GENERAL NOTES

intensive methods of predator control used now. Another cause may be attributed to the declining number of homesteads, small farms, and ranches.

BARRY L. FLOYD' AND MARK R. STROMBERG2, 'Wyoming Game and Fish Department, 1419 E. Pershing Blvd., Cheyenne, WY 82001, and 2The Nature Conservancy, 1603 Capitol Ave., No. 325, Cheyenne, WY 82001. Submitted 2 April 1980. Accepted 19 December 1980.

J. Mamm., 62(3):651-652, 1981

BATS KILLED AT A NORTH FLORIDA TELEVISION TOWER: A 25-YEAR RECORD

Nocturnal migrant birds are killed frequently by colliding with man-made structures; occa- sionally, accounts of these disasters include records of bats (Avery et al., 1980). The most thor- ough study of avian casualties during migration has been at the WCTV tower in Leon Co., Florida, which has been checked for dead birds almost daily since October 1955 (Stoddard and Norris, 1967; Crawford, 1974). During these 25 years (through September 1980) 54 bats of seven species were recovered and we summarize the records here. Specimens are in the Tall Timbers Research Station collection.

Myotis austroriparius.-Total: 1 (16 September 1961). Eptesicus fuscus.-Total: 1 (3 October 1961). Lasiurus borealis.-Total: 10 on 9 dates. Seasonality: August (5); September (1); October (4).

Extreme dates: 17 August 1956-25 October 1964. Specimens: 2. Lasiurus seminolus.-Total: 17 on 16 dates. Seasonality: April (1); May (2); July (1); August

(1); September (5); October (7). Extreme dates: 26-30 April 1970-26 May 1967; 25 July 1963; 5 August 1964-24 October 1963. Specimens: 7. The specimen from 26 May 1967 had 4 embryos (crown-rump length = 19 mm).

Lasiurus cinereus.-Total: 12 on 12 dates. Seasonality: February (1); March (1); October (7); November (3). Extreme dates: 13 February 1959-4 March 1973; 3 October 1967-16 November 1976. Specimens: 7.

Lasiurus intermedius.-Total: 8 on 8 dates. Seasonality: March (1); August (1); September (5); October (1). Extreme dates: 3 March 1971; 24 August 1963-10 October 1963. Specimens: 5.

Tadarida brasiliensis.-Total: 2 (both 4 October 1962). Unidentified.-Total: 3; 16 August 1960, 19 August 1960 (a Lasiurus sp. with 2 L. borealis),

19 September 1962. The 54 bats were killed on 49 nights, 6 in spring and 42 in fall; there was one summer record

(July). Bats apparently hit both the tower and its guywires, and bats were killed on nights with heavy overcast as well as with clear skies: of 48 known nights (excluding the record from 26-30 April 1970), 28 had a mean sky cover of 40% or more; 20 had a mean sky cover of less than 40%. Ten nights had no clouds. The four most frequent species and their mortality on clear and cloudy nights are: L. borealis, 5 cloudy to 4 clear, L. seminolus, 10:5, L. cinereus, 8:4, and L. inter- medius, 4:4. Of 21 specimens, two were noted to be young of the year. All of the species found are resident and breed in north Florida except L. cinereus. Zinn and Baker (1979) discussed the WCTV records of this bat with regard to migration through Florida. L. borealis may be killed often during migration (Avery et al., 1980). Notes by the late Herbert L. Stoddard, Sr., who initiated the WCTV study, state that while recording bird migration data at the WCTV site by focusing a telescope on the disk of the moon (Lowery, 1951), he observed bats apparently mi- grating. Stoddard also observed bats foraging about the tower. The red navigation lights of the tower attract insects, which could account for the presence of some bats.

Van Gelder (1956) proposed that bats are killed because of echolocation failure caused by large numbers of birds in the air during the migration disasters. Bats occur in large bird kills at WCTV (6 of the 49 nights had more than 50 birds killed each) but 16 of the bat kills were on nights when no more than one bird was found. An equally likely explanation is that the bats

intensive methods of predator control used now. Another cause may be attributed to the declining number of homesteads, small farms, and ranches.

BARRY L. FLOYD' AND MARK R. STROMBERG2, 'Wyoming Game and Fish Department, 1419 E. Pershing Blvd., Cheyenne, WY 82001, and 2The Nature Conservancy, 1603 Capitol Ave., No. 325, Cheyenne, WY 82001. Submitted 2 April 1980. Accepted 19 December 1980.

J. Mamm., 62(3):651-652, 1981

BATS KILLED AT A NORTH FLORIDA TELEVISION TOWER: A 25-YEAR RECORD

Nocturnal migrant birds are killed frequently by colliding with man-made structures; occa- sionally, accounts of these disasters include records of bats (Avery et al., 1980). The most thor- ough study of avian casualties during migration has been at the WCTV tower in Leon Co., Florida, which has been checked for dead birds almost daily since October 1955 (Stoddard and Norris, 1967; Crawford, 1974). During these 25 years (through September 1980) 54 bats of seven species were recovered and we summarize the records here. Specimens are in the Tall Timbers Research Station collection.

Myotis austroriparius.-Total: 1 (16 September 1961). Eptesicus fuscus.-Total: 1 (3 October 1961). Lasiurus borealis.-Total: 10 on 9 dates. Seasonality: August (5); September (1); October (4).

Extreme dates: 17 August 1956-25 October 1964. Specimens: 2. Lasiurus seminolus.-Total: 17 on 16 dates. Seasonality: April (1); May (2); July (1); August

(1); September (5); October (7). Extreme dates: 26-30 April 1970-26 May 1967; 25 July 1963; 5 August 1964-24 October 1963. Specimens: 7. The specimen from 26 May 1967 had 4 embryos (crown-rump length = 19 mm).

Lasiurus cinereus.-Total: 12 on 12 dates. Seasonality: February (1); March (1); October (7); November (3). Extreme dates: 13 February 1959-4 March 1973; 3 October 1967-16 November 1976. Specimens: 7.

Lasiurus intermedius.-Total: 8 on 8 dates. Seasonality: March (1); August (1); September (5); October (1). Extreme dates: 3 March 1971; 24 August 1963-10 October 1963. Specimens: 5.

Tadarida brasiliensis.-Total: 2 (both 4 October 1962). Unidentified.-Total: 3; 16 August 1960, 19 August 1960 (a Lasiurus sp. with 2 L. borealis),

19 September 1962. The 54 bats were killed on 49 nights, 6 in spring and 42 in fall; there was one summer record

(July). Bats apparently hit both the tower and its guywires, and bats were killed on nights with heavy overcast as well as with clear skies: of 48 known nights (excluding the record from 26-30 April 1970), 28 had a mean sky cover of 40% or more; 20 had a mean sky cover of less than 40%. Ten nights had no clouds. The four most frequent species and their mortality on clear and cloudy nights are: L. borealis, 5 cloudy to 4 clear, L. seminolus, 10:5, L. cinereus, 8:4, and L. inter- medius, 4:4. Of 21 specimens, two were noted to be young of the year. All of the species found are resident and breed in north Florida except L. cinereus. Zinn and Baker (1979) discussed the WCTV records of this bat with regard to migration through Florida. L. borealis may be killed often during migration (Avery et al., 1980). Notes by the late Herbert L. Stoddard, Sr., who initiated the WCTV study, state that while recording bird migration data at the WCTV site by focusing a telescope on the disk of the moon (Lowery, 1951), he observed bats apparently mi- grating. Stoddard also observed bats foraging about the tower. The red navigation lights of the tower attract insects, which could account for the presence of some bats.

Van Gelder (1956) proposed that bats are killed because of echolocation failure caused by large numbers of birds in the air during the migration disasters. Bats occur in large bird kills at WCTV (6 of the 49 nights had more than 50 birds killed each) but 16 of the bat kills were on nights when no more than one bird was found. An equally likely explanation is that the bats

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652 JOURNAL OF MAMMALOGY Vol. 62, No. 3

simply are not echolocating during migration and they do not detect the tower and its extensive systems of guywires (Griffin, 1970).

We gratefully acknowledge the work of Mr. Stoddard, as well as E. V. Komarek, R. Komarek, L. Neel, and R. A. Norris in collecting and recording the bat casualties.

LITERATURE CITED

AVERY, M. L., P. F. SPRINGER, AND N. S. DAI- LY. 1980. Avian mortality at man-made structures: an annotated bibliography (re- vised). U.S. Fish Wildl. Serv., Biol. Serv. Program, FWS/OBS-80/54:1-152.

CRAWFORD, R. L. 1974. Bird casualties at a Leon County, Florida TV tower: October 1966-September 1973. Bull. Tall Timbers Res. Sta., 18:1-27.

GRIFFIN, D. R. 1970. Migrations and homing of bats. Pp. 233-264, in Biology of bats (W. A. Wimsatt, ed.). Acad. Press, New York, 1:1-406.

LOWERY, G. H., JR. 1951. A quantitative study of the nocturnal migration of birds. Univ. Kansas Publ., Mus. Nat. Hist., 3:363-472.

STODDARD, H. L., SR., AND R. A. NORRIS. 1967. Bird casualties at a Leon County, Flor- ida TV tower: an eleven-year study. Bull. Tall Timbers Res. Sta., 8:1-104.

VAN GELDER, R.G. 1956. Echo-location fail- ure in migratory bats. Trans. Kansas Acad. Sci., 59:220-222.

ZINN, T. L., AND W. W. BAKER. 1979. Seasonal migration of the hoary bat, Lasiurus cinere- us, through Florida. J. Mamm., 60:634-635.

ROBERT L. CRAWFORD AND W. WILSON BAKER, Tall Timbers Research Station, Rt. 1, Box 160, Tallahassee, FL 32312. Submitted 8 October 1980. Accepted 19 December 1981.