Landlords often mistakenly assume that when they see young martins fly
from the housing after it is lowered or when they open a compartment, that these
young are fledgling prematurely. Not true. Often, fledglings will return to
the housing AFTER they have fledged. They may go back to their natal cavity or
they may go into a compartment with smaller young and kleptoparasitize them.
That is, they may sit at the entrance and "steal" all the incoming food, causing
the smaller nestlings to starve or become weakened.. The general rule of thumb
is this: if the birds fly fairly well when they exit, they have probably
already fledged. If they are barely able to stay aloft, and skitter just above
the ground, flying weakly, they have fledged prematurely.
When some nestlings reach about 22 days old, landlords must be cautious while doing nest checks in order to avoid premature fledging. Here is the recommended procedure:
1) Consult last weeks nestcheck record to see which cavities contain
nestling that are 22+ days old. Prepare some entrance hole plugs (socks,
Styrofoam cups, rags, etc.)
2) Lower the housing as slowly and as gently as possible. Talk very quietly or not at all..
3) As soon as the housing is down, quickly and quietly plug all the cavities which contain 22+ day old young. If unsure which cavities contain older nestlings, just plug all the cavities.
4) Conduct the nest check, replugging each cavity (that contains old nestlings) as you go. Do not touch any older nestlings (22+ days) with your hand. Rather, just count heads or use a long blunt probe to separate them enough to count. Remain quiet. Don't rush, but don't dawdle.
5) Tie a 10-12 ft. piece of string to the plugs in the cavities which are left plugged (because they contain old nestlings) Make sure the plugs are positioned so they they will not catch on anything when you attempt to pull them out later. Also, do not push the plug in so tightly that it will be difficult to pull out with the string. Re-raise the housing, as slowly and quietly as possible.
6) Allow the martins to settle down for about 5 minutes, and then pull the plugs by slowly pulling on the strings. Do not jerk the string to pull the plug out, or the string might pull through the plug. Be sure you've pulled all plugs.
I have had great success with this method, and rarely have a premature
fledge. (If I do, it's usually because I was careless.) I've also noticed (as
Kent Justus once mentioned), that incidents of premature fledging seem almost
nonexistent with SREH's. Your neighbors may think you've finally gone nuts,
with your martin housing temporarily looking like a Macy's parade float, but it
Premature Fledging less likely with Routine Nest Checks
In the course of doing field work and visiting many different colony sites over the course of the past few seasons, we’ve noticed that older nestlings (which are close to fledging age) are much less likely to fledge prematurely if they have grown accustomed to the routine of weekly nest checks. Apparently, nestlings become familiar with the experience of being raised and lowered in their housing when it’s done from an early age, and are a lot less "jumpy" or "nervous" about the experience as they get older. Here’s another reason to do regular (5-7 day) nest checks.
Ken Kostka, PMPA