Besides starlings I seem to have brown headed cowbirds. I didn't even know they existed until I dropped two while shooting at a starling. Felt really bad until I read about them.
The female drops eggs in other bird's nests, as many as 30+ per female.
Are brown headed cowbirds a threat to 2" round hole gourds?
2014 8 gourds, 3 pairs nested. Ended w/ 24 total
2015 24 gourds, 22 nests. Lotsa birds!
2016 24 gourds and good activity.
2017 32 SREH gourds. Great activity.
2018 40 SREH gourds. Good finish despite big storm damage. No more dangling gourds.
2019 56+ SREH gourds, all on 3/8 rods. Birds did very well.
2020 56 SREH gourds.
2015 24 gourds, 22 nests. Lotsa birds!
2016 24 gourds and good activity.
2017 32 SREH gourds. Great activity.
2018 40 SREH gourds. Good finish despite big storm damage. No more dangling gourds.
2019 56+ SREH gourds, all on 3/8 rods. Birds did very well.
2020 56 SREH gourds.
-
Dan G
- Posts: 446
- Joined: Thu Jun 12, 2014 7:52 pm
- Location: PA/Bellefonte
- Martin Colony History: Several colonies with in 6 mile radius.
Have had visitor every year 2014-24.
Two large trees removed in fall 2024 and moved T-14 to a more open location.
2025- 1 SY pair. Fledged 2.
2026- no pairs. One daily SYM here daily. Named him Riggs!
I dont think they are a physical threat to adults. I think the issue would be do you want your martins to be feeding a cowbird chick, when that food is meant for young martins. In some 'bug challenged" areas, a chick could starve if a larger cowbird chick was taking their food.
Bellefonte PA
2014, 1st year-a few lookers, no nests
2015-23. Visitors each year. But no pairs.
2024- most active year. 2-4 SY male’s hang out most days.
2025, 1 SY pair. 2 eggs, 2 fledged!! Other martins visited daily.
Still eliminating starlings and sparrows.
2014, 1st year-a few lookers, no nests
2015-23. Visitors each year. But no pairs.
2024- most active year. 2-4 SY male’s hang out most days.
2025, 1 SY pair. 2 eggs, 2 fledged!! Other martins visited daily.
Still eliminating starlings and sparrows.
-
Ed Svetich-WI
- Posts: 815
- 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.
From time to time I have had cowbirds sticking their heads in cavities, more so when I had Trio houses but also with porched gourds. They are common in this area. I have crescent and modified excluder entrances and they have not breached any thus far. I am aware of their predation on many bird species around here and have found their eggs in cardinal and warbler nests.They are protected but the federal government is trapping them under special permits in the national wildlife areas north of here as they attempt to increase the population of the threatened Kirkland warbler which is under pressure by cowbird nest parasitism .
Every time that I see them poking around, I watch them closely just because of their reputation. I have not seen them or heard of them laying eggs in martin nests but it makes me nervous that they are even investigating. They are small enough to enter round entrances. I think shallow nest cavities , such as 6x6, may be at more risk.
I located a study done in Louisiana that documented over 100 bird species parasitised by brown headed cowbirds. Open nests were preferred over cavity nesting birds. They specifically noted that prugne subis was not found to be one of the species targeted.
Ed
Every time that I see them poking around, I watch them closely just because of their reputation. I have not seen them or heard of them laying eggs in martin nests but it makes me nervous that they are even investigating. They are small enough to enter round entrances. I think shallow nest cavities , such as 6x6, may be at more risk.
I located a study done in Louisiana that documented over 100 bird species parasitised by brown headed cowbirds. Open nests were preferred over cavity nesting birds. They specifically noted that prugne subis was not found to be one of the species targeted.
Ed
I think I may have to invest in a knitting needle as my 2" hole gourds do not have inspection hatches.
So they can't get into SREH crescents? This is a good reason for me to stop making 2" hole gourds. The cowbirds are thick this year and the timing is about right for them to "sh*t and git".
So they can't get into SREH crescents? This is a good reason for me to stop making 2" hole gourds. The cowbirds are thick this year and the timing is about right for them to "sh*t and git".
2014 8 gourds, 3 pairs nested. Ended w/ 24 total
2015 24 gourds, 22 nests. Lotsa birds!
2016 24 gourds and good activity.
2017 32 SREH gourds. Great activity.
2018 40 SREH gourds. Good finish despite big storm damage. No more dangling gourds.
2019 56+ SREH gourds, all on 3/8 rods. Birds did very well.
2020 56 SREH gourds.
2015 24 gourds, 22 nests. Lotsa birds!
2016 24 gourds and good activity.
2017 32 SREH gourds. Great activity.
2018 40 SREH gourds. Good finish despite big storm damage. No more dangling gourds.
2019 56+ SREH gourds, all on 3/8 rods. Birds did very well.
2020 56 SREH gourds.
As I remember the female cowbird lays an egg in another birds nest. The cowbird eggs hatch sooner than most other birds. The then larger cow bird chick kicks the other smaller nestlings out of the nest so that the parents feed only the cowbird chick. Not pretty. I don't know what a cowbird egg looks like but if you have 2" holes I would find out and remove any cowbird eggs if they do get in a martin house.
-
Courtney-NC
- Posts: 592
- Joined: Tue Jul 15, 2008 2:28 pm
- Location: Holly Springs, NC
- Martin Colony History: 2009-2015-Helped to manage Raleigh site, 36 cavities
2016- 33 pairs at Raleigh site, 1 pair at home site.
2017- 34 pairs at Raleigh site, 3 pairs + extra SYs at home site
2018- 33 pairs at Raleigh site, 5 pairs + extra SYs at home site
2019 - 32 pairs at Raleigh site, 7 pairs at home site, 2 pairs at new Holly Springs park site
Cowbirds will lay eggs in bluebird boxes, which usually have a 1 - 1/2 " opening, so it would be a good idea to monitor your martin nests as well if you suspect a problem. I have heard of isolated incidents of cowbird eggs in martin nests.
Cowbird egg ID: http://www.sialis.org/cowbirds.htm
Cowbird egg ID: http://www.sialis.org/cowbirds.htm
-Courtney
-------------------
NC Purple Martin Society (PMCA affiliate)
http://www.ncpurplemartin.org
-------------------
NC Purple Martin Society (PMCA affiliate)
http://www.ncpurplemartin.org