General Discussion : Non-kestrel next in boxes - what bird?

We put up several kestrel boxes in 2014. One has been occupied by kestrels 2 years in a row and I see that the male is around now (Ohio).

During cleanout In Jan, I found straw nests in 4 boxes - 3 kestrel boxes and one barn-owl box.

a) In 2 of the kestrel boxes and the barn owl box the nest was loosely woven about 4" high with a nest 3-4" diameter and 3" deep.  All 3 nests looked similar.

b) in the other kestrel box the nest was 4" thick, packed, with a slight ~1/2" indent in the center.

None of the nests had feathers, sticks, egg fragments,

I've searched and looked at pics of OH cavity nesters but found no matches ie. other nests are distinct via mud, moss additions, mud-lining, ...  or are too small.

Starlings have tried to use other boxes but their nests are just piles of sticks.

Any suggestions about what kinds of birds might be utilizing the boxes?


Delorahilleary's picture

My first guess would be house wrens - house wrens tend to be the ones that fill nest boxes with grass, either as a real nest or a dummy nest. House wren presence can indicate that the nest boxes are built in areas with too much tree cover.

However, I can't be totally sure! Sometimes squirrels, bluebirds, and other critters use nest boxes as well. If it happens again, perhaps take a picure, and we could say more for sure.

What kind of habitat are the nest boxes in? That can help narrow it down.'s picture

Thank you for the comments Delorahilleary .  We have wren boxes in use and it doesn't look like a wren nest - wrens have also built in our hose reels, shelves in the workshop, boxes, ....  Most of those have some moss.

And some of the straw is 2-3' long.  A lot for a wren to carry?

Thanks for the remindert about the pic. I planned to do that today.

Interesting comment about the habitat.  That hadn't occurred to me re what other birds would take over.  All of the boxes I mentioned are on barn/shed sides.  Tree cover >25' away.  The box the kestrels used is on a barn peak and they use the trees around to hunt in the open fields around the barn.

We put up several other boxes on trees along field edges and all were used by squirrels, other birds; or broken. Some have holes eaten/pecked out.  I didn't know when I installed them that kestrels didn't want any tree cover.

Thanks again.'s picture

This is the nest that was built in the barn owl box.  It's ~32" wide IIRC.  The bowl of the nest is on the far left.  I'll upload a close-up.

A 2-3' piece of straw seems a lot for a wren to carry.

Most woodpeckers are cavity nesters and the size matches up.  Or a duck.

Delorahilleary's picture

Hiya! Thanks for the picture. Now that definitely looks like a starling nest to me - European starlings are an invasive species that do use similar habitat to kestrels. If you see the adult starlings or otherwise confirm it's a starling nest, that could be removed if you wish. I wouldn't remove any nests without knowing for sure, however. Definitely keep an eye on it!
-Delora's picture

Thanks for the comment. The only starling nests I see here (OH) are roughshod affairs of twigs and bunched grass.  This looks more refined than our starlings.

Also, starlings make a mess around the nest outside; this one is clean.

I have removed starling nests from kestrel boxes and will continue to do so.

Sarah Schulwitz's picture

I love this game! I wouldn't rule out wren...How about Carolina Wren? I've
seen Carolina Wren nests fill up half a Wood Duck box before. Being in a pine
forest, those nests were filled primarily with pine needles with a
distinctive cup. 

Below, I've copied the description of Carolina Wren nests from the Birds of
North America (BNA) website
Notice that straw is listed as one of the materials used! If you are
interested, BNA is a great resource to learn about nests of lots of other
species as well! Good luck on identifying your nest builder! As Delora
mentioned, please do not remove nesting material unless you have positively
identitfied it as built by a species that is not protected.

"Structure And Composition Matter (Carolina Wren Nest)

Cup nest, usually domed with entrance at side; average height above ground
1.8 m (0.7 m SD, /n/ = 393; Cornell Nest Record Cards). Cavity nests may
have partial dome (TMH) or no dome (Laskey 1948 [1] ). Nests often bulky and
constructed loosely of bark strips, dried grasses, dead leaves, oak catkins,
sticks, pine needles, mosses, hair, feathers, light straw, wool clumps, shed
snake skin, paper, plastic, and string ( Thomas 1953 [2] , Oberholser
1974c [3] , TMH). Porch or ramp often leads to nest entrance and may be a
few decimeters in length ( Baumgartner and Baumgartner 1992 [4] , TMH).
Nest has more haphazard appearance compared to Bewick's and House Wren nests
(Baumgarter and Baumgartner and Baumgartner 1992 [5] ). First nests are
often bulkier and have a greater mass than subsequent nests of season
( Ramsay 1987 [6] , TMH)."

From: Haggerty, Thomas M. and Eugene S. Morton. (2014). Carolina Wren (Thryothorus ludovicianus), The Birds of North America (P. G. Rodewald, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America:

DOI: 10.2173/bna.188

Also, take a look at this Carolina Wren nest for comparison:'s picture

Thank you for the reply Sarah Schulwitz and for the wren suggestions.  I was blocked from the BNA site by a login but I found pics of various wren nests online.

We have several house and Carolina wren nests around in boxes, on shelves in the barns,....  Most of the Carolina wren nests are hooded/cavity eg. one is in a plastic pail where I have wood clamps; another in a spare electrical box; another inside a coffee can.

The nest in the barn owl box doesn't look like the typical wren nest - it is all straw, no bits of moss, feathers, short grass,.... as I see in the other wren nests.  But I won't rule the wren out - there were several pics of larger woven nests as you suggest.

This link of yours is great

You wrote "As Delora mentioned, please do not remove nesting material unless you have positively identitfied it as built by a species that is not protected."  Yes, we're careful about this. Starlings are common and easy to ID.

I usually go to Cornell 1st to research a bird.  I find it and most bird sites frustrating:  inconsistent format across species, missing info eg. there's no notes on Cornell that kestrel boxes are best placed on poles/barns - not on trees.

There's no mention of kestrel pellets.  For the 3rd year now:  the male kestrel arrives here, eats in a shed attached to my workshop and leaves several pellets, then moves to a nest when his mate arrives.  This seems like basic behavior that would have been observed and reported.

You can get most of the info you want about birds, but it often takes reading through a dozen sites.  It seems like there'd be more consistency by now.

Posted in General Discussion by 2 years 3 months ago.