Cognitive ornithology: the evolution of avian intelligence

Abstract

Comparative psychologists interested in the evolution of intelligence have focused their attention on social primates, whereas birds tend to be used as models of associative learning. However, corvids and parrots, which have forebrains relatively the same size as apes, live in complex social groups and have a long developmental period before becoming independent, have demonstrated ape-like intelligence. Although, ornithologists have documented thousands of hours observing birds in their natural habitat, they have focused their attention on avian behaviour and ecology, rather than intelligence. This review discusses recent studies of avian cognition contrasting two different approaches; the anthropocentric approach and the adaptive specialization approach. It is argued that the most productive method is to combine the two approaches. This is discussed with respects to recent investigations of two supposedly unique aspects of human cognition; episodic memory and theory of mind. In reviewing the evidence for avian intelligence, corvids and parrots appear to be cognitively superior to other birds and in many cases even apes. This suggests that complex cognition has evolved in species with very different brains through a process of convergent evolution rather than shared ancestry, although the notion that birds and mammals may share common neural connectivity patterns is discussed.

Figure 1

(a) Classic view of the avian telencephalon, in which the greatest proportion of the cerebrum is classified as striatal in origin (dark grey shading), compared to the smaller extent of the pallium (light grey shading). (b) Recent view of the avian telencephalon, in which the majority of the cerebrum has been reclassified as pallial in origin (light grey shading) compared to the smaller striatum (dark grey shading). Adapted from Jarvis & Consortium (2005). Abbreviations: CDL, area corticoidea dorsolateralis; E, ectostriatum (classic) or entopallium (revised); HA, hyperstriatum accessorium (classic) or hyperpallium apicale (revised); HP, hippocampal complex; IHA, interstitial nucleus of the hyperpallium intercalatum; L2, field L2; LPO, parolfactory lobe; OB, olfactory bulb.

Figure 2

Scatter plot comparing body size (g) with volume of telencephalon (mm³) in Old and New World corvids. The regression line is the line of best fit passing through the origin. Old World corvids (crow, rook, jackdaw, magpie, chough, red-billed blue magpie, European jay, Clark's nutcracker) are represented with black symbols. New World corvids (western scrub-jay, pinyon jay, Mexican jay) are represented with white symbols. Data taken from Basil et al. (1996) and Healy & Krebs (1992).

Figure 3

Drawings of frontal sections through the telencephalon of (a) a rat and (b) a pigeon, with details of the similar connections patterns within (a) the laminated cortex of rats and (b) the laminated Wulst of pigeons. Adapted from Medina & Reiner (2000). Abbreviations: ac, anterior commissure; ACC, nucleus accumbens; cc, corpus callosum; Cl, claustrum; DB, diagonal band of Broca; EN, endopiriform region; HA, hyperpallium apicale; HD, hyperpallium densocellulare; HP, hippocampal complex; IHA, interstitial nucleus of the hyperpallium intercalatum; LC, lateral cortex; lv, lateral ventricle; M, mesopallium; N, 66 nidopallium; NC, neocortex; OB, olfactory bulb; S, septum; STR, striatum; TU, olfactory tubercle.