Annual Cycle of the Black-Capped Chickadee: Seasonality of Food-Storing and the Hippocampus

Abstract

Previous research presents a mixed picture of seasonal variation in the hippocampus of food-storing black-capped chickadees. One field study has shown an October peak in hippocampus volume, although laboratory studies conducted to determine whether photoperiod regulates this seasonal growth have failed to find changes in the size of the hippocampus. To resolve the discrepancy between field and lab reports we examined caching activity, hippocampal volume, and neurogenesis in adult male black-capped chickadees at four times over the annual cycle: October, January, April and July. We found that more birds stored food in October than at other times of year, but did not observe a significant change in the size of the hippocampus over the annual cycle. Telencephalon volume, however, was larger in October than in July. Hippocampal neuronal recruitment showed a significant peak in January, but there was no seasonal change in neuronal recruitment in the adjacent hyperpallium apicale. These results indicate that there might be seasonal variation in the recruitment of new neurons into the hippocampus of chickadees without overall seasonal change in hippocampal size.

The Avian Hippocampal Formation and the Stress Response

“…A similar pattern was found in ventricular zone cell proliferation in hand-reared marsh tits ( Poecile palustris ) during the first few months of life [Patel et al, 1997]. Keeping wild-caught chickadees in captivity for 6 weeks (or even one week [Hoshooley et al, 2007]) in the autumn removes this rostrocaudal pattern in neurogenesis, with the largest decrease in the rostral pole and the smallest decrease in the caudal pole [Barnea and Nottebohm, 1994]. Similarly, the volume reduction following captivity in black-capped chickadees is more noticeable in the rostral 2/3 of the HF than in the caudal 1/3 [Tarr et al, 2009].…”

Hippocampal adult neurogenesis: Its regulation and potential role in spatial learning and memory

“…Indeed, this approach eliminates various confounds associated with laboratory studies, namely the unnatural, controlled laboratory environment and the use of stress-inducing spatial tasks that often require extensive training. To this date, field studies have mainly focused on assessing hippocampal adult neurogenesis in animal species that display food hoarding behaviors, including bird species such as the black-capped chickadee ( Parus atricapillus ) (Barnea and Nottebohm, 1994; Barnea and Nottebohm, 1996; Chancellor et al, 2011; Hoshooley and Sherry, 2004; Hoshooley et al, 2006; Hoshooley and Sherry, 2007) and mountain chickadee ( Poecile gambeli ) (Freas et al, 2012; LaDage et al, 2010), as well as rodent species such as the eastern grey squirrel ( Sciurus carolinensis ) (Barker et al, 2005; Lavenex et al, 2000a; Lavenex et al, 2000b), red squirrel ( Tamiasciurus hudsonicus ) (Johnson et al, 2010), Siberian chipmunk ( Tamias sibiricus ) (Pan et al, 2013), and yellow-pine chipmunk ( Tamias amoenus ) (Barker et al, 2005). It is of importance to note that both avian and mammalian hippocampal formations originate from the reptilian dorsomedial cortex.…”

Neurogenesis in the Adult Avian Song-Control System

“…New neurons added to the HC at different times may allow anatomical separation of memories formed at the different times (i.e., pattern separation [Clelland et al 2009]). Hoshooley and Sherry (2007) measured food-caching behavior and neuronal addition to the HC in captive black-capped chickadees at four times of year. They found that food caching was greatest in October, and that neuronal recruitment to HC 1 wk after BrdU injection reached a peak in January.…”