03 - foraging videos

Yesterday I left home before dawn and got back after dusk, so I did not hear or see the magpies, but this morning at 6:30am IA, IB, and PA sat on the power pole singing, and then the juveniles flew down to forage in the street and the front garden, while PA took off in another direction.

I finished this week's study materials and watched the videos about resource competition on the train yesterday, and am going to devise a simple test to see if and what kind of competition there might be, when the magpie parents come around again 
(I have not seen PB for a while, and PA is not around much either), and/or when other species might be competing for food. 

We learned that there are three types of strategies with regard to competition for resources:
- exploitative competition: this occurs when consumption of a resource such as food, water, space, mates, etc makes the resource unavailable to others within or outside of the species
- resource defence: this is a strategy that makes sense if the costs for monopolisation of a resource are smaller than the benefits reaped
- resource sharing: this is the best strategy if cooperation reduces cost of territoriality

A few months ago, when I was feeding IA and IB, so I could catch them and snip off the fishing line they had entangled around their respective feet, there rarely was competition between the juveniles over the strips of meat on the saucer, even though on one occasion IA uttered a song that must have been territorial, as IB backed off until IA had a good feed. I have also observed them calling each other when food was around, and leaving a scrap or two for the late arrival.
Whenever the parents were around, there was a clear hierarchy, with PA being the first to choose, and then PB could take a feed. PA picked on the juveniles, especially IB who was a bit cheeky and tried to get the first scrap quickly, before PA could get to it. Whenever PA pecked at IB, the juvenile turned on his back in a submissive position. I only saw a peck in IA's direction once from PA, and IA quickly went to hide under one of the chairs outside, and puffed itself up while sitting close to the ground, rather than taking the submissive posture.

So when IA came into the garden early this morning, with IB not far behind, I used some seeds to test whether the siblings would compete for these. The video is below.

As you can see they seem to be quite comfortable sharing, and it was also interesting to observe the juveniles' reaction to various bird calls in the second half of the video. I could not see the parent birds, but IA and IB seemed to react to one set of calls in particular.

Just a few seconds after IA had flown off, I saw what had gotten IB's attention earlier. So here below is a clip where you can see another species, a pied butcherbird (Cracticus nigrogularis), coming into the picture. You can also see IA making a cameo appearance at the beginning, before setting off to forage for worms around the corner. Butcherbirds and magpies belong to the same Cracticidae family and are closely related.