Just a random thought

[ShawnK]

This is a hypothetical scenario -

What if a PM Landlord with 100% occupancy and has 100 pairs of birds and they all fledged 4 each, that would be 400 fledged from that colony. My understanding is that only 20% usually return to the site to nest where they were born. That would means 80 birds would be trying to return to this site leaving 320 that are going to make their way somewhere else either starting a new colony somewhere or joining an existing one.

Now I know not all 80 are going to make it back and all of the original 100 pair are not going to make it back either. This is just one colony out of how many others are out there.

My point is this is - where are all of these birds when so many good people are trying for years? Where do they go?


Just my ramblings.

Shawn

[taxidermy lady]

Yeah I ask that to! Seems they wouldn't be so picky ha! I think a lot of the young get killed or eaten, lake of experience. I would think Brazil is more a threat to our martins than North America. Seems like more remote areas. But "Bear" got through it, the survival dude! big snakes down there too!

[John Miller]

Couple of challenges. Only 30 percent -- maybe a little more -- of the fledges survive one year.

Second hurdle for us...it's not enough to sustain the species to just put up housing. It's a start, but I think many martins that could nest in available housing some years will just hang out, visiting occupied housing. Especially the sub adult females. Birds don't always do what we think is best, but we keep trying, putting up housing in the most attractive ways we know, and taking care of existing colonies.

John

[Matt F.]

One theory I've read about (and agree with), is the percentage of sub-adult Martins that return to their natal colonies to nest, is dependent on the size of their natal colony.
We know that sub-adult (SY) females would much prefer to mate with strong, fully "decorated", adult (ASY) males.
We also know, that most of the time, it's the SY male "bachelors" that fan out, and look to start their own, new colony.
It is going to be much harder for an SY male to attract a female to a new location, if there is a large colony nearby bustling with ASY males.

Large colonies that continue to add housing, are going to be a huge vacuum for its returning subbies, and it no doubt going t retain a much larger percentage of them, compared to very small colonies.
Conversely, large colonies that are not adding new housing, are going to be forcing a LOT of returning Martins to fan out, and start new colonies (a process called "forced dispersal").

[DornCounty]

One theory I've read about (and agree with), is the percentage of sub-adult Martins that return to their natal colonies to nest, is dependent on the size of their natal colony.
We know that sub-adult (SY) females would much prefer to mate with strong, fully "decorated", adult (ASY) males.
We also know, that most of the time, it's the SY male "bachelors" that fan out, and look to start their own, new colony.
It is going to be much harder for an SY male to attract a female to a new location, if there is a large colony nearby bustling with ASY males.

Large colonies that continue to add housing, are going to be a huge vacuum for its returning subbies, and it no doubt going t retain a much larger percentage of them, compared to very small colonies.
Conversely, large colonies that are not adding new housing, are going to be forcing a LOT of returning Martins to fan out, and start new colonies (a process called "forced dispersal").

I've read several good stories where long time landlords who are maxed out will actually reduce their cavities until the subbies arrive. This forces the ASY's to colonize the less popular locations.

[daveh]

I hear Brazil is going thru a real serious drought. No bugs flying hence birds are dying.

dave

[ShawnK]

Thanks for all the replies everyone.

It sounds like it would be beneficial to other "potential landlords" if the martins had to setup housing outside the larger colonies "Forced Dispersal". Fortunately in my area I do not have any "large colonies" around me.

I've also wondered about the situations where maybe someone has a colony but can no longer take care of it and has no one to help so the boxes never get put up in the spring or maybe that person passed away. That may be where someone reports a sudden influx of martins either to a first time or existing landlord.

I know for myself I am taking care of my father-in-laws martins after he passed away. It is a great learning experience for me while I am still trying to attract and start my own colony. His is not a very big colony but about 10 pr. He is about 9 miles away from me and you never know, just maybe I could get some of those that I fledged from his houses.

Shawn