Brightsmith and Villalobos • CLAY LICK FEEDING STRATEGIES OF PARROTS 
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Lick Aggregation Dynamics. —Groups of birds 
on the lick were fluid; large numbers of birds flew 
regularly between the surface of the clay lick and 
the adjacent trees. Some birds took pieces of clay 
and carried them to the trees for consumption. 
Thus, the maximum number of birds on the lick at 
any one time was substantially less than the total 
number of birds in the area. Entire feeding 
aggregations often abandoned the lick in response 
to alarm calls. No apparent cause for the alarm 
(n = 1.060 disturbances) was detected in 90% of 
cases and the birds usually returned to the lick 
almost immediately. Documented causes of dis¬ 
turbance were rockslides (4%). raptors (2%), 
other large birds (2%). and people or boats (1%). 
The large parrot aggregations formed on 97% 
of mornings (n = 71) and accounted for 80% of 
the total lick use. Additional birds flew directly to 
the lick once the first birds landed, and numbers 
on the lick increased rapidly (152 ± 85.2 
individuals on the lick 10 min after start, n = 
65 mornings). Birds continued to arrive in the area 
and perch in the trees even after the first birds 
began to use the lick. At least 951 ± 262 birds 
(range = 791-1,428; n - 6 mornings) arrived per 
morning of which 92% were species that joined 
the large parrot aggregation (874 ± 260 birds, 
range = 621-1,336; n = 6 mornings). The daily 
maximum number of birds simultaneously on the 
lick in the large parrot aggregation averaged 192 
- 86 (range = 24 to 497, n = 69 mornings). The 
large parrot aggregation used the lick for 59.6 ± 
19.2 min (n = 46 mornings). 
The three large macaw's used the lick in the 
early morning as part of the large parrot 
aggregation (50% of total early morning lick 
use) or in aggregations dominated by large 
macaws (49% of total early morning lick use. 
Table 1). The aggregations dominated by macaws 
formed on 46% of 71 mornings and accounted for 
of the total lick use. The number of birds on 
the lick increased within the first 5 min (12 ± 9 at 
first detection, n = 28 mornings) and remained 
fairly stable thereafter (14 ± 7, n = 11, 10 min 
uher first detection). The average maximum 
number of individuals was 17 ± 10 (n = 33 
mornings). About 10% of the total birds that 
arrived in the vicinity of the lick were large 
macaws (96 ± 24 birds, range = 66-122. n = 6 
homings). The large macaw aggregations lasted 
19 - 13 min (n = 33 mornings). 
The parakeet aggregations formed on 47% of 71 
roomings and accounted for 5% of the total lick use. 
The majority of the birds in the parakeet aggrega¬ 
tion were flocking parakeets and these flocks were 
restless, usually remaining on the lick for only a few 
minutes before taking flight and returning to the 
lick or adjacent trees. The average number of the 
birds on the lick, despite these fluctuations, 
remained fairly stable with time (27 ± 25 birds, 
n = 35 mornings. <5 min after descending to the 
lick vs. 23 ± 21 birds, n - 8 mornings, 10 min 
later). About 36% of all birds arriving at the lick 
were species that joined the parakeet aggregation 
(340 ± 240 birds, range = 95-653, n = 6 
mornings). The maximum number of birds on the 
lick in parakeet aggregations averaged 40 ± 26 
(range = 3 to 138, n = 34 mornings). The parakeet 
aggregation used the lick for 16.2 ± 11.4 min 
( n = 34 mornings) before they dispersed. 
Spatial Distribution. —The clay lick was >1 km 
in length. However, 85% of the total clay lick use 
occurred on only four small areas, totaling only 
18%' of the exposed cliff. Each aggregation 
regularly used the same few lick areas. The large 
parrot aggregation used two sections with exposed 
clay 9.8 to 15.2 m and 1.4 to 8.3 m above the cliff 
base. Neither section had vegetation immediately 
adjacent to the area used by the birds. The large 
macaw aggregation used two tall center sections 
of the lick with exposed clay 7.8 to 15.7 m high. 
Both were isolated from surrounding vegetation. 
Large macaw aggregations did not form on the 
lower portion of the lick. The parakeet aggrega¬ 
tion used the far left edge of the lick almost 
exclusively. This section had exposed clay 8.6 to 
16 m high and trees immediately adjacent to it. 
Lick Use by Other Pssitacines,— The White- 
bellied Parrot was uncommon on the lick 
(Table 1). It was difficult to detect when arriving, 
but apparently arrived in groups of up to 10 
(Gilardi and Munn 1998; DJB, pers. obs.). This 
species did not depend on joining with other birds 
to use the lick. Small groups perched in the trees 
on the left edge of the lick and remained vigilant 
while a few individuals at a time descended to the 
lick (2.8 + 2.0 individuals, n = 23). This species 
usually used the lick in monospecific groups 
(47%) or with the parakeet aggregation (36%, 
Table 1). This species also use the lick until 
-1000 hrs. well after termination of the early 
morning activity (Brightsmith 2004). 
DISCUSSION 
Aggregation Membership. —Clay lick use was 
dominated by large mixed species aggregations 
