SHORT COMMUNICATIONS 
637 
TABLE 1. Raptor counts by species at Concepcion Watch Site, Bolivia during austral autumn 2009 (10 Mai 6 Api). 
Species 
Migralion peak 
Largest flock 
Total 
Counl 
Dale 
Size 
Dale 
Black Vulture Corag\ps atratwf 
747 
104 
14 Mar 
40 
14 
Mar 
Turkey Vulture Cathartes ultra' 
26 
6 
17 Mar 
4 
Apr 
king Vulture Sarcoramphus papa'' 
30 
13 
17 Mar 
12 
1 / 
Mar 
Western Osprey Pandion haliaetu s" 
5 
2 
17 Mar 
Hook-billed Kite Chondrohierax uncinatus b 
2 
2 
25 Mar 
80 
20 
Mar 
Snail Kite Roslrliamus sociabilis c 
396 
130 
23 Mar 
Rufous-thighed Kite Harpagus diodon 1 ' 
12 
6 
2 Apr 
2.000 
29 
Mar 
Mississippi Kite Iclinui mississippiensis' 
5.571 
2,507 
29 Mar 
Lone-winged Harrier Circus bujfonf 
1 
1 
19 Mar 
Rufous-thighed Hawk Accipiter erythroncmiu.C 
12 
7 
15 Mar 
Great Black Hawk Buleogallus urubitinga' 
2 
1 
14 Mar 
Savanna Hawk B. meridionatis' 
1 
1 
27 Mar 
Swuinson's Hawk Buteo swainsoni" 
4 
2 
29 Mar 
White-tailed Hawk B. albicaudatus' 
1 
1 
29 Mar 
Yellow-headed Caracara Milvago chimachima' 
2 
1 
11 Mar 
Southern Crested Caracara Caracara plancus' 
14 
5 
28 Mar 
Unidentified 
153 
Totals 
6,979 
" Nearciic-Neoiropie migrant. 
Neotropic-Intra-tropical migrant. 
' Unknown migrant. 
rainy, I identified all migrating raptors at the 
count site using Swarovski 10 x 50 binoculars. 
I scanned the southern sky in a 180 degrees arc, 
from east to west, to locate migrants. Raptors 
were considered migrating if they appeared on the 
horizon and flew north past the watch site using 
powered or soaring flight. Black Vulture ( Cora- 
gyps at rains), Turkey Vulture (Cathartes aura). 
and Snail Kites (Rostrluamis sociabilis) arc 
common in the study area, and 1 identified these 
species as migrants only if they passed the lookout 
from the south using unidirectional I light and 
Hying high. Data were collected hourly using the 
standardized daily report protocol of Hawk Migra¬ 
tion Association of North America (Dunne et al. 
1986). I selected days with consistent high numbers 
of birds counted to document migration timing. 
Wind speed and ambient temperature were record¬ 
ed using a Kestrel 20(H) Pocket Weather Station 
(Nielsen Kellerman, Chester. PA. USA). 
Raptor Identification. The following field 
marks were used to identify species of raptors: 
underwing and upperwing color patterns, flight 
silhouette, and position of the wings in different 
Hying modes. I consulted raptor Held guides 
(Clark and Wheeler 2001, Ferguson-Lees and 
Christie 2001) as needed. 
RESULTS 
Raptor Counts.—) counted 6,979 migrating 
raptors of 16 species at Concepcidn Watch Site 
(Table 1). The Mississippi Kite was the most 
common species representing 80% Of = 5,571) of 
the individuals counted, followed by Black 
Vulture with 11% Of = 747). and Snail Kite with 
5% Of = 396). Unidentified raptors accounted for 
2% Of = 153). The remaining 2% (ft =112) were: 
Turkey Vulture Of = 26). King Vulture ( Sarcor- 
amphus papa, n = 30), Western Osprey (Pandion 
Imliaetus, n = 5), Hook-billed Kite ( Chondro- 
hi eras uncinatus, n =2). Rufous-thighed Kite 
(Harpagus dindon. n = 12), Long-winged Harrier 
(Circus buffoni. n = 1). Rufous-thighed Hawk 
( Accipiter erythronemius, n = 12), Great Black 
Haw'k ( Btileogallns urubitinga, n = 2), Savanna 
Hawk (B. meridionatis, n = I), Swainson’s Hawk 
(Buteo swainsoni, /i = 4). White-tailed Hawk ( B. 
albicaudatus, n = 1), Yellow-headed Caracara 
(Mileage chimachima, n — 2), and Southern 
Crested Caracara (Caracara plancus, n = 14) 
(Table I ). I also recorded migrating non-raptor 
species from the lookout, including 36 Maguari 
Storks (Ciconia maguari), and u flock of 1 1 
Anhinga (Anhinga anhinga). I also recorded 
thousands of Bam Swallows ( Hirundo rustica) 
