Oyster Shells ??

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Hanover Bill
Posts: 633
Joined: Thu May 14, 2009 3:10 pm
Location: Pennsylvania/Hanover Township
Martin Colony History: 2009 & 10 - 0
2011 & 12 - Visitors
2013 - 2 pr. fledged 9
2014 - 3 pr. fledged 13
2015 - 7 pr. fledged 27
2016 - 15 pr. fledged 72

Are the Manna Pro Oyster Shells available at Tractor Supply alright for Purple Martins? Reading the label, it sounds like they are mainly for chickens, but I was wondering if they are safe for the Martins? If not where do you get crushed oyster shells for Martins?

Hanover Bill.
2009 & 10 - 0
2011 & 12 - Visitors
2013 - 2 pr. fledged 9
2014 - 3 pr. fledged 13
2015 - 7 pr. fledged 27
2016 - 15 pr. fledged 72
Ed Svetich-WI
Posts: 810
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.

Actually, oyster shells have been shown to produce more martin nestlings than the use of egg shells. The study was done by Jamie Hill of the PMCA a number of years ago. Oyster shells are all that I have used for years. They are clean, readily accepted and a 50# bag will last for years. The cost should be about $10 to $12 for the bag. Type in oyster shells in the Search function and you will find a long string about the study results.

Posts: 2174
Joined: Mon Apr 10, 2006 6:07 pm
Location: PA/Avis
Martin Colony History: The 1972 St. Agnes flood wiped out all the Martins in my area. One day, in 1997-98, 5 or 6 Martins landed on the power wires crossing my back yard. I had no house for them. They kept coming back day after day. We got a martin house a few weeks later & they have been coming back every year since. I average 12-15 pair per year.


I tried oyster shells, which a lot of it is actually crushed coral, and my colony refused to eat it. Many of the pieces are like small rocks & too big for a martin adult or chick to swallow. I use crushed egg shells. Both contain about the same amount of calcium. Calcium is not only required to produce a firm egg shell, but also is important for bone growth & development.

The crushed oyster shells & coral is most often used in reef tanks. People that raise chickens often use it as well. I'd buy a small bag & try it to see if your colony will eat it.

Egg shells are easy to do. Just save them or acquire them from a local diner or restaurant. Rinse well & place on a parchment lined baking sheet. Bake at 250 degrees for around 20-25 minutes or until dry, but not browned. Let cool & crush them into about 1/4 inch size pieces.

I also found a couple sites that sell crushed egg shells if you can't do your own:

https://www.mysafebirdstore.com/PLUCKER ... R_LB..html


Toy in PA
PMCA Member
Posts: 806
Joined: Thu Apr 04, 2013 3:30 pm
Location: OH/New Concord

i go thru 100 lbs a year
the pms love them i dont use the ones at tractor supply they are twice the cost and are bigger then the local feed stores
2015 69 pairs 418 eggs 396 fledged
2019 I have 148 openings now
2016 100 pairs 600 babies fledged added another t-14 and have 126 openings now
2015 Jun 24 360 babies and 58 eggs also found one that had died
2017 632 babies 11died and 20 were killed by hawks
2015 74 pairs and 9 eggs 5/14
2010 3pairss
2018 651 babies 5 hawk kills 11 floater kills 25 died in houses and 610 fledged

2014 80 pairs 283 babies 282 fledged one died
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