Why no decrease in tree swallow population?

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LonesomeDuck
Posts: 59
Joined: Tue Nov 10, 2015 5:04 pm
Location: Arcadia, IN
Martin Colony History: 2016- Some visitors on my Trendsetter 12, no nesting pairs yet.
2017- More visitors, still no nesting pairs yet.
2018- Added Troyer Horizontal gourds and moved house to more open location. One nesting pair of subadults! 2 eggs, 1 egg hatched.
2019- added Gemini gourd rack. 2 pairs, 10 eggs, 10 hatched.

There seems to be lots of discussion here recently regarding theories of why the barn swallow and purple martin numbers are down significantly this year. I can confirm the reduction in barn swallow numbers here as we have several dozen most years but only have seen 2-3 this year so far. Can't confirm the purple martin population trends here yet as I don't have an established colony. However, I have probably 2-3x as many tree swallows as last year. It seems if the issue was some broad based problem with South American habitats that the tree swallow population would have been adversely affected along with the barn swallows and purple martins?
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Carlton
Posts: 1959
Joined: Tue May 17, 2005 6:42 pm
Location: Florida/Deerfield Beach
Martin Colony History: I moved to South Florida, from Delaware, in August of 2015.

I care for a 6 condo Sunset House as well as two Deluxe Gourd Racks, with 24 Chirpynest/Excluder gourds, along a canal in Pompano Beach, Florida.


At Quiet Waters Park, nearby in Deerfield Beach, I care for a Deluxe Gourd Rack with 12 TVG's. I also care for a Deluxe Gourd rack with 12 Excluder gourds with Modified Excluder entrances. I am substituting 6 Chirpynest boxes for 6 of the Conley II entranced gourds in 2026.

At another local park, Tradewinds Park in Coconut Creek, I care for a Trendsetter 12, 5 gourds rack with 60 Excluder gourds with Modified Excluder Entrances and 1 Deluxe Gourd Rack with 12 Troyer Vertical Gourds with Starling Stoppers over the Conley II's to keep out smaller starlings.

Tree swallows do not migrate very far. They stay along the coasts all winter, eating bayberries and such, ranging from NC to FL. Rainy cold spells are not as hard on them as they can switch to berries unlike martins. They can nest in a wider variety of cavities since they are considerably smaller.
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jhcox
Posts: 801
Joined: Thu May 26, 2016 9:23 am
Location: tennesse
Martin Colony History: Started colony in 2014. 0 pairs
2015 0 pairs
2016 0 pairs
2017 0 pairs but visitors
2018 1 pair fledged 5
2019 10 pair
2020 25 pair
2021 42 Pair
2022 60 Pair
2023 72 Pair
2024 74 pair
2025 78 pair

I can confirm that the TS population is drastically higher here in the east TN area I have probably 8 to 10 times as many TS as last year and they are just now starting to try to build nest. And the BBs have eggs already and 1 box has 3 in it that are about to fledge. Still waiting on the Subadult PM. I have only seen at my site 1 adult female and 2 adult males. But they didn't stay around long.

JHCox
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LonesomeDuck
Posts: 59
Joined: Tue Nov 10, 2015 5:04 pm
Location: Arcadia, IN
Martin Colony History: 2016- Some visitors on my Trendsetter 12, no nesting pairs yet.
2017- More visitors, still no nesting pairs yet.
2018- Added Troyer Horizontal gourds and moved house to more open location. One nesting pair of subadults! 2 eggs, 1 egg hatched.
2019- added Gemini gourd rack. 2 pairs, 10 eggs, 10 hatched.

Carlton wrote:Tree swallows do not migrate very far. They stay along the coasts all winter, eating bayberries and such, ranging from NC to FL. Rainy cold spells are not as hard on them as they can switch to berries unlike martins. They can nest in a wider variety of cavities since they are considerably smaller.
Good point. I didn't realize that tree swallows don't migrate to South America. So that would suggest that something bad has happened there, or else the barn swallows and purple martins are just taking their time this year migrating further north for some reason.
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handyman315
Posts: 300
Joined: Thu May 12, 2016 11:03 am
Location: SW Ohio
Martin Colony History: Colony established May 20, 2017 after three unsuccessful years. Persistent and aggressive Tree Swallows plagued the site, but beyond learning - and practicing - to control them, was the return in 2017 of a 2016-SY-M previously unable to find a mate. As a handsome ASY-M, he brought along two females and a swagger that soon put the Tree Swallow issue to rest. As the anchor pair, he and his mate hatched all six of their eggs into fat and healthy babies into what settled in to be a three-pair, flourishing new colony with up to 11 birds total, including 3 SY-M trouble makers.

Same here (SW Ohio), i.e., an over-abundance of Tree Swallows, but yet to even see a Barn Swallow (a normal year would see at least 3 or 4 pair).

Also not an established PM colony, but in prior years have had MANY ASY visits. This year - one, so fast and fleeting that I might have imagined it.

Likewise, no subbies yet.
2023-42 Nests, 197 Eggs/Babies
2022-48 Nests Fledged 203
2021-43 Nests Fledged 185
2020-31 Nests Fledged 133, three early deaths due to cold & rain
2019-19 Nests Fledged 84
2018-11 Nests Fledged 48, ASY-M Arrived April 6, Despite Snow & Cold, Joined Soon by Mate & Two Adult Pairs
2017-3 Nests Fledged 13, FIRST-YEAR LANDLORD! Resident SY-M from 2016 Returned (as ASY-M) on May 20. At Least 11 Adult Residents
2016 Late-Arriving SYs, Resident Lone SY-M
2015-14 Many Visits
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William Bagwell
Posts: 24
Joined: Wed Oct 19, 2016 1:23 pm
Location: North Central Georgia USA
Martin Colony History: Long interested in Purple Martins, pole up 2017 retired 2024 and trying harder this year!

Do not have Martins yet :-( And only saw my first Tree Swallows this year after playing the dawn song. (They did not stay! :) )

Where I work has a bunch of Northern Rough-winged Swallows and have noticed no decrease in their numbers this year. Just looked and while they migrate, they do not go as far south as Martins.

Perhaps something did happen? Either in Brazil or here in the US during a time that effected Martins but not Northern Rough-winged Swallows.
Pole up 2017, retired (and trying harder!) 2024, Purple Martins since ???
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Thais G
Posts: 93
Joined: Mon May 05, 2014 6:37 pm
Location: CT/Darien
Martin Colony History: Started at unsuitable location in 2008. Many lessons learned since. Two tentative locations: Rogers International School and the "Fish Church" (downtown.) One pair in 2015; no fledglings though. No pairs 2016.

If something happened, it was spread over large areas without one noticeable area of impact/fatalities because I am Brazilian and searched over news and "Brazilian internet" (in Portuguese) - there were no reports of birds found dead or anything like that. I think they are just late. I know many of you said the TS have been back in mass, but I just - finally! - got mine at the school TODAY. Usually at this time they are well into nesting!! I was SO GLAD to see them - the students have been looking forward to their arrival.
Thais Gherardi
Wannabe Landlord in Stamford, CT (2 tentative sites):
- Rogers International School (S&K barn since 2013; Alamo House installed 2016)
- "Fish Church"/downtown Stamford (Alamo House installed 2016)
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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.

Traditionally, blue bird houses were spaced 100 yards apart since blue birds are territorial. Often, martin enthusiasts are also blue bird advocates. As a result, they build blue bird houses,a lot of houses that they unknowingly place too close together. Studies have shown that in such cases, many more tree swallows than blue birds are produced. I was guilty myself until I read the research, some of which was done here in Wisconsin. I removed half of my blue bird houses and spaced the remaining ones further apart. The result has been more blue birds nesting and fewer tree swallows. I placed several of my blue bird houses on a nearby farm well away from any buildings and widely spaced. In the several years since, every house has been occupied by blue birds. Not one has been used by tree swallows. Here at home, two blue bird pair have successfully defended their nest box against tree swallows.

Since tree swallows are less impacted by an absence of insects, as Carlton correctly stated since they can eat berries, they can move in and colonize areas where exclusive insect eaters are delayed. Since more tree swallows are being produced by the over abundance of incorrectly placed blue bird houses, there are more and more. Tree swallows have been here since March 22nd. Quite a vicious circle.

The martins will arrive when the weather normalizes, whatever normal is. The still have site fidelity.

Have a good martin season.

Ed
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