Broken Legs May Signal Owl Predation
From: Kent Justus, Mt. Vernon, AR
Date: 6/7/01
Time: 4:08:07 PM
Comments
I’ve been around the blocks a long time in this martin interest. I’ve seen a lot of things and learned a lot of things about martin behavior simply by sitting out and observing my martins. I’ve had an epiphany recently concerning broken legs in purple martins. Let me explain. Years ago when I first started hosting martins (1978 to be exact) I used Trio martin housing exclusively. These are high quality houses that last forever if maintained properly. However, back then in the late 70’s and 80’s there was no such thing as enlarging compartments or much questioning of the 6"x6" compartment size in these Trio houses.
Over the years I noticed and logged in my yearly notes that I had several martins, usually one or two a year that would come up with a broken leg. I also had martins with missing feathers and other injuries that stood out in my mind from those days. I used to draw conclusions about the broken legs by considering that martins have rather thin, weak legs and claws when compared to other songbirds of similar size. Just look at the leg of a Starling when compared to a martin’s and it looks like a pro wrestlers arm compared to a weakling’s. I thought that over the course of the season that this was "normal" to have martins come up with broken legs due to their apparent fragility. However, over the years I gradually began shifting my housing to very large natural gourds and through the late 80’s into the 90’s and now into the 21st century it has occurred to me that I no longer regularly see broken legs on martins in my colonies. I started wondering why. Then, something happened the other day that sparked my thoughts on this subject. A friend called in Little Rock and said that he had a male martin "die" at night when trying to get into his compartment on a TG-12 Trio Grandpa martin house. I explained to him that martins don’t just die when trying to enter their compartments and that something must have killed it. He had a 2"x4" owl guard on the house per my advice a couple of years ago. Anyway, he removed the dead martin and examined it and sure enough found a deep slash on the back of its neck AND A BROKEN LEG. Suddenly, it occurred to me that perhaps during my early years of being a martin landlord and remembering several adult martins that showed up during the nesting season with broken legs that perhaps instead of chalking it up to not being careful when exiting a compartment or a fight with another martin or Starling that perhaps these martins had barely survived an encounter with an owl at night.
My theory is that the owl’s talon might have grabbed onto the martin’s leg and during the process of trying to pull the martin through the entrance hole it broke the martin’s leg but the martin struggled free and scrambled to the back of the compartment and survived the encounter. This dead martin that my friend found certainly showed evidence of the owl encounter with the slash to the back of the head and neck that certainly killed the martin. However, while trying to pull the martin through the 2"x4" hardwire cloth it got stuck and owl dropped it only to leave it there. I have also heard of headless martins being found behind owl guards where apparently the owls talon cut the martin’s head off when it tried to pull it through the guard and left the lifeless martin body on the porch of the house for the landlord to make a grisly discovery the following morning.
Stop to consider the next time you see a martin with a broken leg that this may have been caused by an owl attack. Perhaps all of those early years when I saw martins with broken legs in my own colony that they were being maimed by owls at night and barely surviving the encounters. Back then I probably wouldn’t have known if martins were disappearing or not. If this is the case you need to ensure that you have enlarged compartments (6"x12") or large gourds (10" or larger diameter) as well as owl guards to keep the martins as safe as possible. It is in your best interest as a thoughtful martin landlord to do everything within your power to ensure the safety of your birds. Sometimes however, providing guards and enlarged compartments isn’t enough if the martin flushes out of the house and tries to escape, but this will definitely reduce owl predation and possibly maiming of adult martins at your site.
A martin that has been maimed with a broken leg has to struggle to maintain its balance at night when roosting and perching during the day and slowly draining it of valuable energy. These martins are almost certainly doomed as I never recall seeing a martin return from migration with a broken leg. This always happened during the course of the nesting season. Something to consider and ponder. Please protect your martins from owls by providing larger compartments and owl guards.
Kent Justus / Mt. Vernon, AR
