Northern Harrier Struggling to Expel a Pellet

 

Except for owls, all raptors have a crop for excess food storage.  The parts of the prey that are indigestible are formed into a pellet in the gizzard and then regurgitated out of the mouth.  These pellets contain hair, feathers, exoskeletons and sometimes (in the case of owls especially) the bones of their prey.  I’ve noticed with many raptor species that expelling a pellet can be a difficult process, bordering on traumatic.  Such was the case with this juvenile male Northern Harrier.

I was watching this bird through my lens but not planning on getting any quality photos because the bird was strongly side-lit.   But when he began trying to expel a pellet I couldn’t resist clicking away.  Because of the side-lighting and relatively soft focus the images are not of high quality but I thought the behavior was interesting enough for a blog post anyway.  All of the photos in this series are posted in the order that they were taken.

 

 The beginning of the struggle to expel the pellet 

 

Here the harrier is shaking his head from side to side to try to dislodge the pellet

 

But with the effort he begins to lose his balance on the perch 

 

And almost falls  over backward 

 

He begins to recover 

 

And then falls forward 

 

Begins to recover again 

 

Still recovering 

 

Recovered, but still with the pellet stuck in his mouth 

 

And finally the pellet has been expelled. 

As luck would have it my buffer had filled up and I missed the shot of the pellet flying out.

For these birds to go through such effort and apparent trauma to regurgitate the pellet must be an indication of the great advantage to them of not having their digestive systems deal with all of that “roughage”.  I also wonder if this behavior may have been partially selected for as another weight saving device for flight, though I’ve been unable to verify that.  Either way I think it’s a fascinating behavior.

Ron