The Hippocampal Complex of Food-Storing Birds

Abstract

Three families of North American passerines – chickadees, nuthatches and jays – store food. Previous research has shown that memory for the spatial locations of caches is the principal mechanism of cache recovery. It has also been previously shown that the hippocampal complex (hippocampus and area parahippocampalis) plays an important role in memory for cache sites. The present study determined the volume of the hippocampal complex and the telencephalon in 3 food-storing families and in 10 non-food-storing families and subfamilies of passerines. The hippocampal complex is larger in food-storing birds than in non-food-storing birds. This difference is greater than expected from allometric relations among the hippocampal complex, telencephalon and body weight. Food-storing families are not more closely related to each other than they are to non-food-storing families and subfamilies, and the greater size of the hippocampal complex in food-storing birds is therefore the result of evolutionary convergence. Natural selection has led to a larger hippocampal complex in birds that rely on memory to recover spatially dispersed food caches.

Hummingbirds have a greatly enlarged hippocampal formation

“…The expansion of the HF in birds is generally associated with better spatial memory [7,8,14,15] and given the ability of hummingbirds to remember a range of spatial -temporal features of their flowers, the gross enlargement of the HF of hummingbirds probably reflects their spatial memory. That said, there are other factors that could have contributed to HF enlargement in hummingbirds.…”

“…We measured the HF and telencephalon on every fourth section of the hummingbird and swift specimens with a 200 mm grid using the same HF borders as earlier studies [14,15]. The error coefficients [11] of the HF and telencephalon measurements were 0.021 (range ¼ 0.014-0.040) and 0.009 (range ¼ 0.008-0.024), respectively.…”

“…Although there are criticisms regarding the combination of data from disparate sources in comparative studies [7,16], it is only by including data for a broader range of species that we could determine with confidence whether hummingbirds have larger HFs than other birds. Furthermore, all of the literature data that we compiled used the same criteria to determine the borders of the HF [15,17].…”

Recent advances in behavioral neuroendocrinology: Insights from studies on birds

“…Although less dramatic, recruitment of neurons into the adult hippocampus is also observed for food caching songbirds, and the hippocampus is critical for accurate cache retrieval (Sherry & Vaccarino, 1989). Scatter-hoarding species are found within a number of songbird families, including the Corvids (crows and jays), Parids (tits and chickadees), and Sittids (nuthatches; Krebs et al, 1990), and of these, the neuroanatomy of the black-capped chickadee (Poecile atricapillus), has been studied the most.…”

Performance of four seed-caching corvid species in the radial-arm maze analog.

“…When the ratio of hippocampal volume to telencephalon volume was calculated for each of these four species and compared on the regression line of this ratio for a wide variety of New and Old World corvids (Krebs, Sherry, Healy, Perry, & Vaccarino, 1989;Sherry, Vaccarino, Buckenham, & Herz, 1989), nutcrackers had the largest relative hippocampal volume.…”