Date: 11/1/18 11:09 am
From: Tait, Mag <mtait...>
Subject: RE: [birders] What is the bulge?
I learned about caching from this list a couple of years ago. It explained something that I had long wondered about; the sudden large increase in the sunflower seeds disappearing in the fall when there was still natural food, followed by less as winter came.
I have never seen a jay with a bulging throat. I will definitely be looking!

Thanks for brining this up and the explanation!

Mag

From: Janet Hinshaw <jhinshaw...>
Sent: Wednesday, October 31, 2018 9:30 PM
To: <suzeev...>
Cc: <winerat...>; <birders...>
Subject: Re: [birders] What is the bulge?

Jays and nutcrackers are known for caching acorns and seeds for later retrieval. They have a throat pouch, not a crop, that they carry food in. This is the bulge you are seeing. They are very good at remembering where they hid the food, and are able to retrieve most of their caches. They cache seeds with the shells on, which keep them fresh until eaten. Here is some information from Birds of North America. Would you like to work that hard to gather enough food for the winter?


Usually prefers smaller acorns over large ones (Scarlett and Smith 1991<https://birdsna-org.proxy.lib.umich.edu/Species-Account/bna/species/blujay/references#REF5119>), but may prefer larger acorns in some years under certain circumstances (Bartlow et al. 2011). Usually harvests 1-5 acorns or up to 15 beechnuts at a time, depending on size of fruit (Darley-Hill and Johnson 1981<https://birdsna-org.proxy.lib.umich.edu/Species-Account/bna/species/blujay/references#REF5081>, Johnson and Adkisson 1985<https://birdsna-org.proxy.lib.umich.edu/Species-Account/bna/species/blujay/references#REF5095>, Bartlow et al. 2011). Transports acorns by storing 2-3 in its distended throat and anterior esophagus (Johnson and Webb 1989<https://birdsna-org.proxy.lib.umich.edu/Species-Account/bna/species/blujay/references#REF5096>), with one more each in mouth and bill-tip (Figure 2<https://download-ams-birds-cornell-edu.proxy.lib.umich.edu/api/v1/asset/24993181>). During 3 days, jays made 1270 and 1959 visits to 2 pin oak trees and removed 3175 and 4897 acorns, respectively (Steele et al. 2010).

Caching distance may be relatively short (<150 m [Bartlow et al. 2011] or up to several km (KGS). Upon arrival at a cache site, an individual places all acorns in a pile, then buries them singly within a radius of 1-3 m. Usually covers the cache with a dead leaf or pebble. Observations of 6 radio-transmittered birds indicated each cached 3,000-5,000 acorns in one autumn (C. S. Adkisson pers. comm.). One report of 4 jays caching dead mice in winter (Whitford 1996). May cache a calcium source (e.g., egg shells) in fall (Dhondt and Hochachka 2001).

Janet Hinshaw Ph: 734-764-0457
Bird Division Collection Manager Fax: 734-764-4080
Univ. of Michigan Museum of Zoology
3600 Varsity Dr.
Research Museums Center
Ann Arbor, MI 48108 USA

On Oct 31, 2018, at 8:24 PM, 'Suzanne (Moses) Vedder' via Birders <birders...><mailto:<birders...>> wrote:
I've seen my Jay's do the same thing. I believe it is a full crop. They fly off, regurgitate some of it and cache it.

Suzanne in Big Rapids
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On Wed, Oct 31, 2018 at 7:17 PM, Sally K. Scheer
<winerat...><mailto:<winerat...>> wrote:

My sister in the UP (Brimley) has a very active feeder. Lots of interesting birds on her acreage that used to be a hunting camp full of wonderful variety. She is a keen observer of all things natural and is puzzled by this bluejay that seems to have an extra bulge below his beak. It is present every time he visits the feeder and differs from other bluejays that also visit regularly. We wondered if it was a full crop? It’s there every time he visits and doesn’t seem to enlarge as he vigorously scoops up black sunflower seeds.

IS it a full crop? If so, why does it not appear to change size as he stuffs more seed in?

Sally Scheer

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