Placement of crescent opening

Welcome to the internet's gathering place for Purple Martin enthusiasts
Post Reply
Posts: 28
Joined: Sun Mar 23, 2014 9:54 am
Location: TX/Katy

Making new houses. The base is a Western cedar board 6” wide and 15” long. The outer deck is 6” wide x 5”. The inner house is 6” x 10” x 6” tall. Can you picture that?

Can the base of the crescent opening be the deck itself? This means the top of the crescent would be 1-3/16” from the deck. Or should I raise it up some? If so, how much should it be raised? The detachable crescent openings will be made from 1/8” thick white PVC plastic.

I will have 8 houses that can be raised and lowered by rope. Houses are finished just need to get the entrance holes attached. Birds are on the way!!!!

Dave Duit
Posts: 1737
Joined: Tue Nov 25, 2003 2:02 pm
Location: Iowa / Nevada
Martin Colony History: In 2020, 60 pair with 285 fledged youngsters. 83 total cavities available, 58 Troyer Horizontal gourds and 4 modified deep trio metal house units, 1 fallout shelter, owl cages around all units. Martin educator and speaker. President and founder of the Iowa Purple Martin Organization. Please visit and join.

Hi Mike,
The bottom of the crescent should be raised1/8th to 1/4 inch of the base floor. Keep in mind that if you plan on having a subfloor insert in the cavity, the crescent bottom should then be raised to accommodate for the floor.
Mite control, heat venting, predator protection and additional feeding during bad weather add up to success.
Posts: 757
Joined: Fri Mar 11, 2011 1:09 pm
Location: Manitoba/Altona
Martin Colony History: six pair in 2014, have grown to 52 pairs in 2017.

Under the housing section, on this website, " Starling-resistant entrance holes (1-3/16” tall x 2-3/4” to 3” wide) should be placed so the bottom of the entrance is flush with the compartment floor, or not more than 1/4” above it." I prefer the 1/4 inch above the floor, but either will work.
2011- first year trying, a few visitors.
2012-One ASY pair, raised two young, lots of subby visitors. So thankfull.
2013-daily subby visits.
2014-Six SY pairs
2015-18 pair, 83 fledglings
2016-36 pair, 147 fledglings
2017-52 pairs, 192 fledglings.
2018-60 pair, 246 fledglings.
2019-59 pair, 238 fledglings.
Chris B
Posts: 378
Joined: Sun Jun 01, 2014 4:10 pm
Location: AL/Toney

Flush with the bottom of a box? Then where does the nest material go? On my gourds, as well as the plastic Big Bo V2, the bottom of the crescent is about 1 1/2 or more above the bottom, so there is room for a nest bowl and the entrance isn't blocked.
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.
Posts: 415
Joined: Mon Mar 16, 2009 2:45 pm
Location: Missouri/Ava

The bottom of the nest cavity should always be lower than the porch floor in my opinion. For this reason I try to use tunnels on all my housing and then can have the entrance flush with the porch. It has been proven that when they are flush it is much more resistant to a Starling breach. Since you may need to raise your entrance, I suppose an added thickness of material could be added to the porch if it didn’t add too much weight. I have done that in the past on some housing with success. Further down on this forum one can see some tunnels that we made.
Posts: 2932
Joined: Wed Mar 29, 2006 8:49 am
Location: Indiana/Henry Co.

When I built my T 14 I made it so my porches sit a little higher then the floor on the inside. My thought was that the crscent could be closer to the porch on the outside helping to keep starlings out, but from the inside the bottom of the crescent would be higher making it a little easier for the Martins to get out of the needed to quickly for some reason. I ended up making removable trays so I’m glad I did it that way because the trays don’t block the entrance.
I also opted to get the SREH plates to screw onto the front of the house instead of trying to cut it into the wood itself. I didn’t trust myself to cut them perfectly and if you are just a little too small the Martins can’t get in, a little too big and the starlings will get in. I just cut square holes in the door and screwed the plates over them. They are cheap and have held up fine for 10 years or so.
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.
Post Reply