Persistence in Foraging: When Do Bullfinches Abandon Unprofitable Seeds?

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Abstract
Captive bullfinches (Pyrrhula pyrrhula) were studied in order to find out if and why they abandon fruits after lengthy unsuccessful attempts to crack open the husks. For three kinds of fruits, the probability of husks cracking remained constant throughout handling. Bullfinches feeding on ash and sunflower fruits dropped many, failing to retrieve most of those that dropped in the first 12 seconds after picking up (thus identified as 'rejected'), but only 20% of those dropped later ('abandoned'). The incidence of abandoning fruits was higher in samples taken from ash trees with less variably-sized fruits, and when sunflower fruits of a particular size were presented alone, rather than in a mixture of other sizes. Both results support the idea that unsuccessful handling provides information allowing birds to revise their estimates of fruits' profitability. However, abandonment did not occur after a consistent period, as predicted. Rejection of fruits during the first few seconds of handling was a more important food selection mechanism than either visual assessment before handling, or later abandonment. Captive bullfinches (Pyrrhula pyrrhula) were studied in order to find out if and why they abandon fruits after lengthy unsuccessful attempts to crack open the husks. For three kinds of fruits, the probability of husks cracking remained constant throughout handling. Bullfinches feeding on ash and sunflower fruits dropped many, failing to retrieve most of those that dropped in the first 12 seconds after picking up (thus identified as 'rejected'), but only 20% of those dropped later ('abandoned'). The incidence of abandoning fruits was higher in samples taken from ash trees with less variably-sized fruits, and when sunflower fruits of a particular size were presented alone, rather than in a mixture of other sizes. Both results support the idea that unsuccessful handling provides information allowing birds to revise their estimates of fruits' profitability. However, abandonment did not occur after a consistent period, as predicted. Rejection of fruits during the first few seconds of handling was a more important food selection mechanism than either visual assessment before handling, or later abandonment.