Introduction to the Maya Project Introduction to The Selva Maya Principal Agents of Tropical Deforestation The Maya Project Components - Activities and Results


Despite its name, the Bat Falcon 
(Falco rufigularis) eats mainly 
small birds and large insects 
such as dragonflies.

Description and Results

The following account of our research activities follows the outline just given. For each topic, we describe the associated conservation challenges, give some background knowledge on the topic, describe our research activities, and give a brief synopsis of our results.

3. Toward the Documentation of a Tropical Forest Food Web

The study of the structure and function of food webs is in part a rather esoteric branch of the field of theoretical ecology. However, food web structure and function are also important topics in applied conservation biology. Although the functional role of predators in ecosystems is far from fully understood, there is little doubt that predators of various sorts play key roles in producing what we regard as normal community structure and function.

The Laughing Falcon 
(Herpetotheres cachinnans
is a snake-eating specialist.

Changes in the abundance of different predators have been shown or suspected to lead to various sorts of ecological imbalances. For example, in the absence of large predators, smaller predators have been found in some cases to increase in number--a phenomenon sometimes termed "mesopredator release ." In turn, the proliferation of small and medium-sized, generalist predators is believed to have resulted in increased rates of bird nest predation, both in fragmented, suburban habitats in the U.S. (Wilcove 1985) and in tropical habitats isolated by human activities (Loiselle and Hoppes 1983). In tropical forests, there is some evidence that the disappearance of large predators from isolated forest tracts may reverberate through the community, resulting even in changes in the species composition of the tree community (Terborgh 1992, Terborgh and Wright 1994).

We consider it very likely that food web structure and function undergo dramatic changes as landscapes are subjected to progressive deforestation and habitat fragmentation. We predict that food web structure in isolated forest fragments is related to factors such as fragment size and degree of isolation (i.e., whether organisms move freely through the surrounding habitat matrix), and may differ radically from that observed in continuous forest. However, we are a long way from knowing whether this prediction will prove true; little is yet known of food webs in areas of continuous forest, and even less is known of food webs in habitat fragments.

Several Neotropical raptors
 include many reptiles in their 
diets, even the venomous 
fer-de-lance (Bothrops asper).

Probably the most complete documentation of the food web of a tropical forest to date is that of Reagan and Waide (1996) for the Luquillo Experimental Forest in Puerto Rico. However, even in their detailed study, the diet of birds is reported in quite general terms, and only five species of raptorial birds occur in this much-simplified island avifauna. Even the best-studied Neotropical mainland sites--La Selva and Monteverde, Costa Rica; Barro Colorado Island, Panama; and Manu, Peru--have not been the site of thorough analyses of food webs among the vertebrates, although a long-term study of diets of predatory vertebrates is under way at La Selva (Greene 1988). A recent paper (Poulin et al. 2001) makes an interesting contribution, documenting the degree to which many primarily insectivorous, non-raptorial birds in Panamanian forest included small lizards and frogs in their diet.

Ornate Hawk-Eagles and Collared 
Forest-Falcons (Micrastur 
) included  many 
Keel-billed Toucans  (Ramphastos 
) in their diets.

For no tropical raptor community has a thorough analysis of community-wide diets been achieved. To date, the closest thing to such a study is that of Robinson (1994), in which he describes habitat use, hunting behavior, and diet of the raptors of Manu National Park, Peru. Voous (1969) provides a somewhat similar overview of raptor diets in Surinam.

At Tikal we collected dietary data for 20 raptor species, totaling more than 7,000 prey items identified at least to the level of Class. Sample sizes were as follows:


Number of Diet Items Documented for Raptor Species at Tikal

Study species

Diet items documented 
(identified at least to Class)

Swallow-tailed Kite (Elanoides forficatus) 1,496
Double-toothed Kite (Harpagus bidentatus) 550
Plumbeous Kite (Ictinia plumbea) 655
Hook-billed Kite (Chondrohierax uncinatus) 67
Bicolored Hawk (Accipiter bicolor) 218
Crane Hawk (Geranospiza caerulescens 181
White Hawk (Leucopternis albicollis) 210
Great Black-Hawk (Buteogallus urubitinga) 130
Roadside Hawk (Buteo magnirostris 192
Crested Eagle (Morphnus guianensis


Black Hawk-Eagle (Spizaetus tyrannus) 85
Ornate Hawk-Eagle (Spizaetus ornatus) 325
Barred Forest-Falcon (Micrastur ruficollis) 405
Collared Forest-Falcon (Micrastur semitorquatus) 206
Laughing Falcon (Herpetotheres cachinnans 747
Bat Falcon (Falco rufigularis) 1.405
Orange-breasted Falcon (Falco deiroleucus 105
Mottled Owl (Strix virgata) 61
Black-and-White Owl (Strix nigrolineata) 73
________________________________________ _______________________
Total 7,211
Average per study species 379 + 428 (SD; n = 19)
Median per study species 206

Our analyses of these data from the standpoint of the raptor community's ecology are still underway. Without a doubt, these data will provide the most detailed portrait to date of the diet of a tropical forest raptor community.

Literature Cited, Toward the Documentation of a Tropical Forest Food Web


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This section has been developed for The Peregrine Fund by
Asana Draper
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Last Revised:  12/10/08