Biology Reference
In-Depth Information
Table 18.1.
Characteristics of bird faunas of five tropical regions based
on standardized counts in nine matching habitat types. Density and
morphological space indexes refer to the overall bird fauna. The nearest
neighbor index is the mean of values for eight habitats.
Total species
Morphological
Mean nearest
Density index
1
space index
2
neighbor index
2
Locality
in counts
Panama
135
15.3
5.90
0.19
Tr inidad
108
17.0
6.37
0.19
Jamaica
55
24.5
5.07
0.18
St. Lucia
34
23.3
5.69
0.26
St. Kitts
20
19.8
3.41
0.29
1
See Cox and Ricklefs (1977).
2
See Travis and Ricklefs (1983).
1977;Travis and Ricklefs 1983). Data were first collected on the diversity
and abundance of species across nine habitat types in central Panama,
Tr inidad, Jamaica, St. Lucia, and St. Kitts.These locations included a con-
tinental area and West Indian islands with progressively smaller land bird
faunas (table 18.1). The number of bird species encountered in the vari-
ous habitats varied almost sevenfold, being greatest in Panama and least in
St. Kitts. Nevertheless, indices of total bird density showed that increased
abundance of individual species compensated fully, or even overcompen-
sated, for the reduction in number of species (Cox and Ricklefs 1977).
Analyses of the morphology of passerine species in the Panama-to-St.
Kitts study were carried out by Travis and Ricklefs (1983). Data were
obtained on eight measurements: body length; wing, tail, tarsus, and mid-
dle toe lengths; and beak length, width, and depth. Multivariate analyses
were carried out to determine the overall degree of difference among
species in various communities and the five localities. For the five locali-
ties, the combined mensural characteristics occupied almost the same total
morphological space (table 18.1). St. Kitts, with the fewest species, was
somewhat of an exception, with the space occupied being substantially
less.The average multivariate distance between species was greater for the
bird communities of St. Lucia and St. Kitts than for communities of the
larger islands and Panama. For the community types in a given location,
the average multivariate distance between species tended to be very sim-
ilar. Evidence was thus strong that ecological interactions among species
were setting some limits to coexistence, especially in the small islands
where density overcompensation appeared to exist.
