If Coley’s Late, Will Mate Wait?

Coley sure has me baffled.  In order for him to have reached Jamaica Bay by his usual arrival time of March 15th, he would have to have departed Colombia around February 21st (a week ago, now), and certainly no later than the end of February.  Yet as of 10am on March 2nd, he was still in Bird Marsh. While we wait for liftoff, let me answer questions about the delay and its likely consequences.

Why do you think Coley has delayed his migration north this year?

Since we do not know exactly what triggers the migration process in Ospreys heading north in the northern spring, we cannot say for sure.  However, whatever the process is, there is certainly a range or window when he may begin that is unique to him.  This window could be several weeks.  With the winter that we have been having with snowstorm after snowstorm, I am glad that he has not departed.  It would be hard on him to arrive in Jamaica Bay with winter still in full swing.

What will Coley’s mate do if she arrives before him? 

The longer the time interval between mates arriving on the breeding site, the more likely it will be that the first arriving mate will attract or be attracted to a new mate. Yes, Ospreys do mate for life as far as we know, but that bond needs to be reinforced each spring by the arrival of the second mate.  If too much time elapses, the instinct to wait for their mate wanes, and they will accept another mate since the instinct to breed is far greater  – and more important – than the instinct to wait for a mate that may have perished over the winter.

So Coley arrives to find that his mate has a new mate – what happens then?

In most cases, the late returning bird will drive off the new bird as the bond between the old mates will be stronger than the newly formed bond between the old mate and the new mate, especially if the new mate is a young bird. We often see three Ospreys on a nest and conflicts between two of them early in the nesting season. These conflicts are usually short in duration and no one gets hurt in the process.  However, once I found an adult Osprey dead in the nest while two adults went about their business of egg laying and rearing young.  I do not know if the dead bird was a former mate or an intruder.

Below is a map of Coley’s most recent, and quiet, behavior in Colombia; our next report should show him heading home.

Thanks again for your input and support.

Coley and Dr. Bob Signing off.

Bull’s eyes = Osprey’s location every hour.
Lines = Sequence of locations in time (not the actual flight path)

Click the Sat(ellite), Ter(rain) or Earth buttons on the map for alternate views. The Earth view requires you to have the free Google Earth software on your computer. For a larger map, go to Google Maps or download the KML file to view in your copy of Google Earth.


  1. Thanks for the update. I’ve been thinking of Coley and wishing him safe passage.

  2. What a great blog :) We are avid kayakers and generally outdoorsy people (in spite of living in NJ 😉 and we always enjoy seeing the ospreys :)

  3. What are the chances of tracking Coley’s mate in the future? We learn so much! Absolutely fascinating.

    • Hi Dolores. Female Ospreys are not typically tracked with GPS. The tracker Coley wears is similar to a backpack, with telfon ribbons connecting at his chest. Because the females spend so much more time sitting on the nest than males, scientists worry the ribbons could put extra pressure on the eggs and they don’t like to put the young at any danger.

      Her journeys will remain a mystery for now.

  4. Ah, so nice to hear that some folk still value a gal’s right to maintain some measure of mystery!