If you’ve ever spent time watching House Sparrows (Passer domesticus), you might have noticed just how, well, squabbly they can be. Just today, I was out walking the dog, and a group of three came screaming (in flight and in sound) out from a pruned cedar shrub, flew across the sidewalk and screamed back into another shrub. They’re social little birds and use that sociality to their advantage–often relying on others to find food to eat. Fights between birds erupt over a number of different reasons (just like us, really) and food is often a source of conflict.
A recently-published paper in the journal Animal Behaviour ((Source Details: Zoltán Tótha, Veronika Bókonya, Ádám Z. Lendvaib, Krisztián Szabóc, Zsolt Pénzesc,and András Liker (2009). Effects of relatedness on social-foraging tactic use in house sparrows. Animal Behaviour, 77(2), 337.)) reports the results of a study that looked at the effect of how being related to another House Sparrow might effect reactions over food.
The study suggests that the more closely related an individual House Sparrow was to another, the less likely there would be conflict (called “Aggressive Joining”) over food. If there was conflict with a close relative over food, less food would be taken from that relative.
Interestingly, there was a sex difference reported that was possibly attributed to the fact that female House Sparrows spread out over a greater distance from their original flock. If a male was to take food without conflict from another bird, it was always from a non-relative bird. Females, however, showed no discrimination when they were taking food (without conflict) from others. Since it is females that spread out, they’re less likely to have close relatives in their new flocks–hence they show no preference for taking food from close relatives or non-relatives.
Perhaps most interestingly, but not surprising, was the acknowledgement that House Sparrow have to be able to recognize and know close relatives:
Since we found differences between several aspects of scrounging behaviour towards close kin and nonkin birds, sparrows are likely to be able to distinguish between genetically closely related and unrelated flockmates.
Since House Sparrows neither breed co-operatively or form family groups, their ability to recognize close relatives is seen as significant.
So, now, while you’re sitting on a patio this summer and see House Sparrows at your feet, spend some time watching them and their reactions over food. You might be able to decide if they’re close relatives or simply strangers.