11 egg clutch

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Posts: 253
Joined: Sat Dec 30, 2017 3:40 pm
Location: Palm City, FL
Martin Colony History: 2018 will be my first try. 6 S&K B09s. 29 eggs - 8 fledged
2019 - 12 Troyer Horizontals with tunnels, 6 S&K B09s and 12 B011s all with tunnels. 43 eggs - 36 fledged
2020 - Rack 1 - 6 B011s, Rack 2 - 24 B011s, and Rack 3 - 24 Troyer Horizontals. All gourds have tunnels, porches and crescent/Conley 11 entrances; racks have predator guards. 161 eggs - 88 fledged

Intraspecific brood parasitism or egg-dumping is a not uncommon practice of wood ducks (especially when wood duck nest boxes are too closely spaced). Brown cowbirds exist because of this habit.
On yesterday's nest check, I counted 11 eggs in one of my 54-gourd colony. Not very familiar with purple martin biology but in my 3 seasons of having this much fun have not seen any posts of clutches this size noted by other land lords. My PMCA Prognosticator Wheel only goes up to 8 eggs (have two 8-egg clutches this season).
Is this "brood parasitism" or just one screwed up, perhaps SY female that entered the wrong apartment and dropped 3 eggs on the existing 8-egg clutch? Are 11-egg clutches so common that experienced land lords consider them unremarkable? I don't know. Any comments from long-time land lords and ladies will be appreciated.
Hope you all are having a good season. Weather has been cooperative here in south Florida. I'm anticipating tripling last year's fledge rate.
Happy Martining, Mike
John Barrow
Posts: 948
Joined: Tue Nov 11, 2003 4:12 pm
Location: Corpus Christi / Sandia , Texas

Mike, Nearly every season we see posts on different forums asking about excessively large clutches of eggs found during a check (eight or more). In nearly all cases these are the result of poor weather, poor incubation (weather related or eggs getting buried among excessive nest material) or the presence of non-viable eggs. In most cases the actual hatch count will be about one half of the total number of eggs counted. While I believe that most of these large clutches are produced by a single pair (with the succession noted in regular nest checks) it is possible that one of the pair is killed and replaced with a new member who lays her own clutch which can be expected to hatch. This scenario, IMO, is less common than incubation failures as set forth above. Likewise, it is not uncommon for SY females to lay eggs in different cavities; however, this does not produce abnormally large clutches in a single compartment. And it would be rare (and uncharacteristic) for two ASY females to lay eggs in a single compartment at the same time.

Last season, Louise Chambers and I had a very late clutch with 10 eggs in it, hosted by an ASY pair at our colony in Sandia, TX. There had been some weather interruptions earlier in the season, but none at this point in time. This, at the time, was one of two active remaining nests at the colony-the other being a SY pair that had 4 eggs being incubated. We anticipated that half of the ASY clutch of ten would hatch. Checking the nest 3 days after the oldest nestling had hatched we found a group of eight nestlings and two non-viable eggs. In Louise's experience (30 years with PMCA in PA and 15 years in TX) and my experience (regular nest checks at mine and many neighboring colonies; and banding thousands of nestlings throughout South and Central TX), this was the first time that either of us had seen a brood of 8 nestlings, and Louise was only aware of one group of eight being reported to PMCA of having fledged in entirety. We shaded both active nests to protect against heat and were able to photo document the weekly progression of the 8- brood nest until all had fledged. We also captured the nestlings from the SY nest (in a tree) and the 8 brood nest (on power lines in the vicinity) the day after the last nestling had fledged on the same morning from each brood.

Member/Mentor-PMCA. I do regular nestchecks and participate in PROJECT MARTINWATCH!! Coordinated 3 geolocator studies-2009, 2010 & 2013. State and Fed licensed bander (retired Jan., 2020)
Posts: 892
Joined: Fri Apr 14, 2017 11:15 am
Location: Corpus Christi Tx
Martin Colony History: 2016- didnt know anything about martins, put up an all wrong house in 2016 and had two come by and inspect all the cavities. Left soon after not to return. Learned what i could on PMCA made adjustments and next year was successful.
2017- 5 pair. 15 fledged
2018- 18 pair. 85 fledged
2019- 17 pair. 81 fledged
2020- 25 pair. 111 fledged
Home colony: mix natural gourds, enlarged compartment house. All SREH.
Satelite colony: Oso Bay Preserve: 12 gourds: PMCA excluder gourds, 6 room trio mino castle with enlarged compartments.
2019: Visitors
2020: 3 pair, 11 fledged
PMCA member

Mj, john,
First, mj, hope all the eggs hatch for you and wish you greatest success! That is a lot of eggs!!! Parents will be busy!

As always sage information, always interested in the environmental impacts and probable reasons for such a big group. will keep an eye on our big group as well and will advise on progress.


One PS. That many eggs would be difficult to incubate, aggrevated by the presence of excessive leaves, so perhaps that is a consideration for you to look for during nest checks. Our birds like ucalyptus (spelling???) Leaves, long and thin, im always pulling them out away from the eggs. Capped eggs as well, watch close for.that.
PMCA member, believer in nest checks, venting, SREH and pest/predator protection.
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