Nest check bonanza and approach to Cowbird egg?

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ron20m
Posts: 446
Joined: Sat Jul 03, 2004 3:01 pm
Location: Oklahoma/Norman

We had some cooler weather and was leaving racks alone, finally did a nest check and was shocked at my egg counts. Out of a total of 33 nests there were 3 with 7 eggs. I usually have one about every other year. There were also another 10 with 6 eggs. What in the world is going on? Just mature birds?

Also one of the 6 nests had a plus one that appears to be a cowbird egg. Speckled like sparrow egg a little darker background color than sparrow and smaller than Martin eggs. I've read that they can come back and check on them. Should I just remove it and see what happens? Or leave it alone until after hatch. Worry about retribution from cowbird.

I had a single Trio house at my home as a kid. When I moved into this house 25 years ago there was a single trio with one pair of martins. I've grown it into three gourd racks. Never had a cowbird egg in 25 years.
flyin-lowe
Posts: 2939
Joined: Wed Mar 29, 2006 8:49 am
Location: Indiana/Henry Co.

I see a lot of cowbirds around my place but have never seen one land on my martin housing and have never seen one enter a martin cavity. I don't recall ever reading about it on here. Do you have SREH? I assumed they would be able to navigate those.
2020 Currently 42 nest, 110 babies, 64 eggs left to hatch(6-22-20) HOSP count-8
2019- 31 Pair over 100 fledged
2018- 15 pair last count 49 fledged
2017 3 SY pair nested, 12 eggs total, fledged 10. 4 additional SY's stayed all summer but never paired/nested.
2016 1 pair fledged 4
2015 Visitors
2014 Visitors
2013 Moved 6 miles away, 1 pair fledged 2.
2012 30 pair fledged 100.
2011 12 pair (11 that nested), 43 fledged.
2010 5 pair, 21 eggs, 16 hatched, 14 fledged.
ron20m
Posts: 446
Joined: Sat Jul 03, 2004 3:01 pm
Location: Oklahoma/Norman

Yes all SREH, but resistant is the word, had a starling this year, probably have a starling get through once a year also.
4th Gen Martin Fan
Posts: 1483
Joined: Thu Jul 04, 2013 1:19 pm
Location: TN/Collierville
Martin Colony History: I have been exposed to purple martin sounds in utero when my mother went out to get my father away from his martin colony.
I played around the martin colony every summer and watched as my father maintained his colony. In the late 50's until the 70's he did not notice European Starlings in south Texas.
When old enough, I helped maintain his colony. My primary task was eliminating English House Sparrows with a 1956 Benjamin 317 .177 air rifle.
When I settled into my own home, I started my first colony with an original Trio Castle and Trio Grandpa. When I moved again, I did not put up any martin houses. Frustration with European Starlings in the Southeast US was overwhelming.
Found PMCA Forum and learned about modern enlarged compartments and SREHs.
Inherited my father's last martin house, a Trio Grandma, modified it to modern specifications and have had good results since then.

That speckled egg with dark background definitely sounds like a cowbird egg.
As you have pointed out, the cowbird may return to investigate its egg and retaliate against the purple martin eggs or nestlings. I would boil the cowbird egg and return it to the nest. Or needle the cowbird eggs and keep it in the nest. Do not wait until the cowbird baby hatches.
The cowbird nestling will dominate the feedings and the purple martin nestlings will not be fed their share and suffer and/or die.

I have seen a cowbird egg in a bluebird nest and seen the consequences of that cowbird's predation.
Mark.
Firm believer in HOSP/EUST Control, Enlarged Compartments, SREHs, Pole Predator Guards, Owl/Hawk Guards, Mite/Parasite Control, Housing Insulation, and Vents for Compartment Cooling.
PMCA Member.
Ed Svetich-WI
Posts: 798
Joined: Tue Jan 13, 2004 10:05 pm
Location: Brooks, Wi (McGinnis Lake)
Martin Colony History: 24 Super and Excluder Gourds on two gourd racks, all SREH. Full occupancy. My philosophy is to maximize fledge % with existing cavities rather than adding gourds to grow colony, thus providing opportunities for new colony expansion. Fledge over 100 nestlings yearly from 24 gourds. Band nestlings in cooperation with state university. 2019 Adendum: Reduced colony size to 12 gourds to focus on more intensive management regimen.

I was wondering if anyone else had an instance where cowbirds had shown an interest in martin nests.I anxiously watched a female cowbird peer into several gourds this spring. There had been several perching on the gourd rack from time to time. It did not attempt to enter but I will be watching to see if it shows any interest after the martins lay eggs. An empty nest would hold no interest to these pests other than a potential target to parasitize in the future. There are already enough challenges to successfully hosting and producing martins.Yet another reason for active management.

A drop of vegetable oil on the shell is all it takes to smother an embryo. It is sometimes used on nusaince geese and others by government agencies.

Have a good season.

Ed
Last edited by Ed Svetich-WI on Sun May 24, 2020 7:03 pm, edited 1 time in total.
johncanfield
Posts: 59
Joined: Mon May 04, 2020 5:13 pm
Location: Texas

We used to get a bunch of cowbirds every spring on our feeders, I would pick off 15 to 20 of them every year then they stopped showing up. I might see two or three now in the spring but they move on. Maybe word got around this wasn't a safe place :wink: . I never saw one on my gourds , I'm not sure they could even fit in the Troyer opening.
John
JJ Ranch
Texas Hill Country
Ed Svetich-WI
Posts: 798
Joined: Tue Jan 13, 2004 10:05 pm
Location: Brooks, Wi (McGinnis Lake)
Martin Colony History: 24 Super and Excluder Gourds on two gourd racks, all SREH. Full occupancy. My philosophy is to maximize fledge % with existing cavities rather than adding gourds to grow colony, thus providing opportunities for new colony expansion. Fledge over 100 nestlings yearly from 24 gourds. Band nestlings in cooperation with state university. 2019 Adendum: Reduced colony size to 12 gourds to focus on more intensive management regimen.

John,

Check out the Migratory Bird Treaty.

Ed
ron20m
Posts: 446
Joined: Sat Jul 03, 2004 3:01 pm
Location: Oklahoma/Norman

Must have had a lot of new arrivals, I now have 53 nests out of 72 cavities. I did not see the comments about how to neutralize Cowbird egg and had removed it. There are now 6 babies about 5 days old so I guess Cowbird didn't run a followup visit.
Did have a single nest of 5 eggs with zero now. Worried about snakes.

And had a nest of six eggs with a dead male inside. Anyone know if female will
try to go it alone or abandon the nest?
bootjack farm
Posts: 67
Joined: Thu Jun 02, 2016 9:30 am
Location: Russell, Pa
Martin Colony History: 9 years of trying hard...finally in 2017 I had 3 pair w/ 11 babies. T-14 +4 w/ 4 Troyer horiz. gourds. Troyer Super System 24. Fast forward to 2020... 64 fledged.

Good point Ed. Technically you can't disturb a Cowbird egg either but try to catch me... I would be concerned about vegetable oil cross contaminating PUMA eggs. I read on the internet (so it must be true) that shaking the egg will destroy the embryo. That seems simple and easy if it works.
I
Northwest PA
SSMartin
Posts: 124
Joined: Sun Jul 21, 2019 6:05 pm
Location: FL

Ed Svetich-WI wrote:
Sun May 24, 2020 9:49 am
John,

Check out the Migratory Bird Treaty.

Ed
Lots of birds on this list of protection have open hunting seasons every year. Cranes, waterfowl, dove, snipe, quail, just to name a few.

Meanwhile cowbirds who thrive on our forest clearing are overwhelming many songbirds who are in threatened numbers. Give it a rest.
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