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Hoarding in the spring by the rook, Corvus frugilegus

Ståhlberg, Mika (2017) BIOK01 20171
Degree Projects in Biology
Popular Abstract
Rooks hoarding in the spring

Rooks are among the species of birds that hoard food for the winter. During autumn the rooks gather nuts, mainly walnuts and acorns, that they hide in caches. Hoarding starts in September and peaks in October. Some hoarding may also occur in November. Rooks are scatter hoarders, which means that they hide their nuts in many small caches, usually containing a single nut. Hoarding rooks often transport several nuts at the same time, carrying them in the beak or under the tongue. Rooks often pilfer nuts from each other's caches, meaning that a caching rook must be on the lookout for other rooks.

My study investigates if rooks who are given access to a large amount of food will hoard in the spring. I also... (More)
Rooks hoarding in the spring

Rooks are among the species of birds that hoard food for the winter. During autumn the rooks gather nuts, mainly walnuts and acorns, that they hide in caches. Hoarding starts in September and peaks in October. Some hoarding may also occur in November. Rooks are scatter hoarders, which means that they hide their nuts in many small caches, usually containing a single nut. Hoarding rooks often transport several nuts at the same time, carrying them in the beak or under the tongue. Rooks often pilfer nuts from each other's caches, meaning that a caching rook must be on the lookout for other rooks.

My study investigates if rooks who are given access to a large amount of food will hoard in the spring. I also investigated if there is a difference in how much the rooks hoarded in comparison to how much they ate, depending on different factors. These factors were whether it was earlier or later during the study, the time of day, location and number of rooks present at the feedings. I examined this by putting out food for the rooks and observing their behavior.

I observed many instances of rooks gathering several nuts, presumably to hoard. I also saw a few occasions when a rook actually cached nuts. I found that the rooks hoarded more during the earlier half of the study, in the afternoon and at one of the locations, in proportion to how much they ate. I did not see a statistically significant correlation between hoarding and number of rooks present, but could see a trend of rooks hoarding more when fewer rooks were present.

My results showed that rooks can in fact hoard during the spring, if given access to an abundance of food. This was somewhat consistent with other studies, where rooks have been observed to hoard during the winter during years with late crops of acorns. It was more surprising that the rooks exhibited more hoarding behavior compared to eating in the afternoon. Earlier studies have shown rooks to exhibit somewhat more intense hoarding activity in the morning.

The fact that rooks hoarded more in comparison to eating when fewer rooks were present is consistent with the fact that rooks avoid having their caches discovered by other rooks. The fact that the rooks of one location engaged in a higher percentage of hoarding than the other is likely related to the fact that there were usually fewer rooks present at that location.

Because there was no way to distinguish between individual rooks it was unavoidable that the same rooks were sometimes observed (and their behavior recorded) multiple times. I tried to compensate this with a large amount of data. However, this was difficult to achieve, since I had to adapt very much to the level of cooperation of the rooks. Sometimes there were simply no rooks on the ground to feed and sometimes the rooks were too shy or uninterested to approach the food.

Handledare: Anders Brodin
Examensarbete 15 hp i biologi 2017
Biologiska instutitionen, Lunds universitet (Less)
Please use this url to cite or link to this publication:
author
Ståhlberg, Mika
supervisor
organization
course
BIOK01 20171
year
type
M2 - Bachelor Degree
subject
language
English
id
8925702
date added to LUP
2017-09-15 11:24:55
date last changed
2017-09-15 11:24:55
@misc{8925702,
  author       = {Ståhlberg, Mika},
  language     = {eng},
  note         = {Student Paper},
  title        = {Hoarding in the spring by the rook, Corvus frugilegus},
  year         = {2017},
}