Indeed, the “bird supermarket” is well stocked with
a wide range of chitin- covered choices. Arthropods
range in size from tiny to noticeably large (think gnats
compared with tarantulas). That expansive size range
matters because it presents a broad food resource
spectrum. Eating insects and other arthropods per se
does not cause speciation, but it does accommodate
increasing avian diversity, because such a broad resource
spectrum promotes specialization. No species eats both
gnats and tarantulas. Insects and other arthropods don’t
want to be eaten by birds. These prey animals require
finding, and that requires a search image. Arthropods
require catching, and that requires a foraging technique.
As described in chapter 11, arthropods are well adapted
to avoid predation through either cryptic or warning
coloration or escape behavior (plate 15- 71). Each insect-
eating bird tends to develop a particular behavioral
repertoire employed in finding, catching, and feeding,
and the bird’s size, behavior, and bill shape evolve to
focus on a particular size range and type of prey. Prey
characteristics provide major selection pressures in
shaping evolution among avian predators.
Bird species compete against one another. The
presence of many insect- eating species cohabiting a
complex ecosystem generates continuous low- level
(also called diffuse) competition within a species
assemblage, keeping each species ecologically adapted
to doing what it alone does best.
Insect eaters can be roughly categorized by overall
feeding method. These are: (1) fly- catching (tyrant
flycatchers, puffbirds, and nunbirds), (2) bark probing
and drilling (woodcreepers and woodpeckers), (3)
foliage gleaning (ovenbirds and many antbirds), and
(4) ant following (some antbirds and others).Puffbirds and Nunbirds: Just Sit and Wait . . .
and Wait
Puffbirds and nunbirds make up the family Bucconidae,
of which there are 35 species. They are most closely
related to jacamars and woodpeckers, and all are
exclusively Neotropical. They feed primarily on insects
captured by darting from a perch and snatching the
prey from a branch or the ground, a foraging behavior
termed a sally strike. And they are patient about it, to
the point of being called “lethargic” by some observers.
These birds will perch (depending on species) from
understory to canopy and remain essentially motionless
as they patiently sit and wait for potential prey.Plate 15- 71. This Peacock Katydid (Pterochroza ocellata),
normally cryptic (its body mimics a leaf ), is here in full display,
not to attract a mate but rather to thwart a potential avian
predator, nature’s version of “shock and awe.” Photo by Sean
Williams.Plate 15- 72. The Black- fronted Nunbird. Photo by Sean
Williams.chapter 15 neotropical birds: the bustling crowd 289