RESULTS
Comparative Structure and Organization of Canopy Bird Assemblages in Honduras and Brazil
Numbers of Detections and Species
From April 2006 to April 2007 DLA conducted 83 censuses in Honduras (56 canopy censuses and 27 ground transects), resulting in 2538 detections of 118 species in the canopy (Table 1). In Brazil, LNN conducted 117 censuses from November 1999 to November 2000, resulting in 9194 detections of 145 species observed in the canopy (Table 1). Our combined data set totals >11 000 detections of canopy birds.
The rarefaction curve for all canopy species in Brazil is asymptotic, indicating that sampling was adequate for the questions posed by the study (Fig. 1a). The all-canopy species curve for Honduras has the same shape as the left side of the Brazil curve but is truncated before it reaches the graduated tail of the asymptote (Fig. 1a), indicating that sampling was also reasonably complete. More importantly, the curves for core canopy species in both Honduras and Brazil reached asymptotes, signaling that sampling of this group was complete and that few core species remained to be added.
TABLE 1. Number of bird species and detections (by sight or sound) from the canopy stratum at Pico Bonito National Park, Honduras, and Manaus, Brazil.
|
No. of Species / No. of Detections | ||||
Method | Censuses | Census hours b | All canopy species | Core canopy species |
HONDURAS |
|
|
|
|
Ground |
27 |
66.7 (2.4 ± 0.56) | 36/300 | 31/294 |
Trees |
56 |
168 (3 ± 0) |
118/2238 |
66/2114 |
Total |
83 |
234.7 |
118/2538 |
66/2408 |
BRAZIL | ||||
Towers (all surveys) |
117 |
351 (3 ± 0) |
145/9194 |
107/8814 |
Towers (reduced set) a |
56 |
168 (3 ± 0) |
138/4575 |
107/4360 |
a Sample size reduced to equal number of censuses in Honduras. |
|
|  |
FIGURE 1. (a) Sample-based rarefaction curves for canopy bird assemblages in Honduras and Brazil. Curves for all canopy species and core canopy species are shown separately. Dotted line around the curve for Brazil depicts 95% confidence interval for all canopy species. (b) Estimates of species richness for all species observed in the canopy (solid shapes) and core canopy species only (hollow shapes) for Honduras and Brazil derived from Chao 1 and Chao 2 estimators, respectively. Shapes represent means and bars encompass 95% confidence intervals. Observed species richnesses in the canopy in Costa Rica and Panama are also shown.
Species richness of canopy bird assemblages in Honduras and Brazil appeared similar. The rarefaction curve for Honduras fell within the 95% confidence interval of the curve for Brazil, indicating that richness of the two sites did not differ significantly (Fig. 1a). Expected species richness for Honduras was approximately 130 species, or 20 species fewer than the 150 species expected for Brazil (Fig. 1b), although the difference was not statistically significant, on the basis of the level of sampling obtained. Observed species richness in Costa Rica and Panama was 86 and 84 species, respectively (Fig. 1b).
