Large Families of Passerine Birds

This one order is very large with many families and will be broken down here into two suborders. The first list is of all families of Suborder Tyranni with 15 or more species--arranged in order of average eye darkness.

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.730 Woodcreepers (25 species)

.729 Tyrant-flycatchers (144 species) DARK-EYED

.713 Antbirds (74 species)

.676 Ovenbirds (34 species)

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.534 Cotingas (59 species)

.429 Manakins (21 species) MID-RANGE

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LIGHT-EYED

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The above list breaks neatly into two groups. The four families in the dark-eyed group mostly eat insects and the two families in the mid-range of eye-darkness mostly eat fruit. Flycatchers are the most aerial of these families. They sit on exposed perches and watch for flying insects that they then pursue and catch in-the open and on-the-wing.

The second list is of all families of Suborder Passeri with 15 or more species in the sample--arranged in order of average eye darkness.

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.829 Swallows (61 species)

.811 Sunbirds (74 species)

.809 Thrushes (140 species)

.796 Wagtails & Pipits (33 species)

.783 American Wood Warblers (68 species)

.781 True Tits (24 species)

.780 Old World Flycatchers (84 species) DARK-EYED

.774 Finches (42 species)

.732 Buntings, Tanagers, etc. (190 species)

.714 Wrens (21 species)

.701 Cuckoo-shrikes (46 species)

.681 Monarch Flycatchers, Wattle-eyes, etc. (87 species)

.680 Flowerpeckers (32 species)

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.645 Larks (43 species)

.644 Honeyeaters (97 species)

.640 Waxbills (109 species)

.636 Thickheads (35 species)

.615 Shrikes (52 species)

.590 New World Blackbirds (50 species)

.557 Bulbuls (70 species)

.551 Weavers (79 species)

.543 Crows, Jays (99 species)

.538 Old World Warblers (198 species)

.529 White-eyes (34 species)

.500 Bowerbirds (17 species) MID-RANGE

.475 Vireos (20 species)

.455 Birds of Paradise (39 species)

.435 Babblers (85 species)

.393 Australasian Warblers (35 species)

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.298 Starlings (62 species)

LIGHT-EYED

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1. The first thing to note is that there are no no light-eyed families of ambush hunters among these many families of passerines of either suborder.

2. The same pattern seen in the Tyranni list of carnivorous families in the dark-eyed category and omnivores/herbivores in the midrange category is to some degree present in this list, also, but there are more exceptions and families with mixed diets that make the comparison less clear-cut than was the case with Tyranni.

3. The most telling thing about this list to me is that the two darkest-eyed families of passerines, swallows and sunbirds, are uniquely similar in behavior to the two darkest-eyed non-passerine families, swifts and hummingbirds. We assume that evolution converged on the most advantageous structural features for these pairs and I would add that it also converged on the most advantageous behavioral traits for which eye-darkness serves as a marker variable.

4. Swallows catch insects in-the-open and on-the wing similar to swifts and nightjars. All three families have very dark average eye-darkness, Dark-eyed, but not as dark on-average are the families of “flycatchers” that also take insects in-the-open and on-the-wing. These birds are less aerial than are swallows and typically sit on an exposed perch to watch for flying insects.

5, With the work of Craig and Hulley (2004), we can see the value of doing eye color studies of the more diverse of these families at the between-species level of analysis. They categorized species into one of three eye color groups: “brown; red; pale (including white, yellow and blue)” and looked for relationships with other species traits, Among their many significant findings are these within the family, Ploceidae (weavers): “A coloured iris [pale or red] is found in all reed-bed inhabitants, most grassland weavers, and about 50% of the savanna and forest species. Eyes are commonly pale in perched feeders, red in ‘gleaners’ and dark in ground-feeding species.” p.586. Within Corvini (crows) they report, “A coloured iris is present in close to 50 % of the woodland and forest corvids, but is exceptional (one species) in birds of open grassland, and thus the association of a coloured iris with feeding in the vegetation, and a dark iris with ground feeding, is clearly linked to these habitat preferences.” p.586.