Sexual Maturity

From: jeanettefromks"at"webtv.net (Jeanette Stamm)
Date: Fri, 5 Jul 2002 13:25:44 -0500 (CDT)
To: BLUEBIRD-L"at"cornell.edu (bluebirds and cavity-nesting birds)
Subject: Re: BLUEBIRD-L digest 184

HI Everybody, I'm new at this so don't know if this will work or not; but we want to know if anyone has ever done any research on whether the first batch of BB's will mate and breed the first year? Or do they have to be at least a year old? We are having a great year but losing some birds to coons and snakes and of course the usual wren and sparrow problems but what great birds these BB are. We have a box down at our city park that has been successful for three years now; every year they have to put up with midget car races and the noise is about a million decibels and of course last night the firreworks. Now this morning I saw both birds; the female was on the nest with 3 eggs and 2 tiny babies but sparrows are threatening them. I am trying to watch but can't spend all my time there. Just praying all will be ok. Thanks for any info you can give us.

From: Bet Zimmerman [mailto:ezdz"at"charter.net]
Sent: Friday, June 18, 2004 11:49 AM
Subject: Age when sexually mature?

How old do female bluebirds have to be before breeding? I tried to do a search on google, and got so many porn hits I gave up :-{ I was wondering because the male who nested in front of my house lost his mate (disappeared) right after their babies fledged. He fed the five fledglings by himself (looking very ragged) and is still sitting near the box, defending it, singing away (sadly I think). I was wondering whether the babies from another pair that nested earlier this spring might be old enough to breed this season. Bet from CT

From: Keith & Sandy Kridler [mailto:txbluebirder"at"sbcglobal.net]
Sent: Saturday, June 19, 2004 8:17 AM
Subject: Re: Age when sexually mature Keith Kridler Mt. Pleasant, Texas

Male and Female bluebirds banded as nestlings in Texas in late August have been trapped breeding and laying eggs the following March. This is about 7 months. I have never heard of banded nestlings from early spring starting their first nest the same summer they hatched out. They would be sexually mature but the days getting shorter in fall would probably prevent them from having the correct hormonal changes. The two bluebirds pictured on the color brochure from NABS are from a photo of Larry Zeleny and these bluebirds were an orphaned "Brother and Sister" siblings from the same nest. Larry raised them and the following spring these two birds mated and raised young of their own. Possibly without a "father" bluebird to drive off the young male the result was incest. At that time in Maryland there were so few bluebirds that incest was probably pretty common with the bluebirds. I am aware of only four long term banding projects where they routinely trap the breeding adults while nesting and only one of these is working with the Eastern Bluebirds that migrate in winter. KK

From: jwick"at"tds.net [mailto:jwick"at"tds.net]
Sent: Sunday, June 20, 2004 11:40 AM
Subject: Re: Age when sexually mature

As a bander, I have also banded nestlings in late August, early September that have been recaptured as breeding females in April of the next year. Ann Wick Black Earth, WI

From: Nature1951"at"aol.com [mailto:Nature1951"at"aol.com]
Sent: Tuesday, July 13, 2004 8:02 AM
Subject: Re: BLUEBIRD-L digest 885

Jeannette, Eastern Bluebirds which hatch this spring or summer will not breed until the following year. The increasing daylight in the spring is one  of the essential triggers for the female to begin producing the right level of hormones required for breeding.  Many of the important events of a bird's annual cycle like breeding, molting, and migration are regulated to a large degree by the changes in photoperiods. Also, birds generally time reproductive time frames to correspond to the peak periods of available food supplies. I sometimes refer to Ben Pinkowski's classic Eastern Bluebird study published in 1974. From that classic work, here is some information related to the ages when females first lay eggs: "Laskey (1943) found that egg laying begins at ages varying from 243 to 370 days. (average of 312 days) Dr. Pinkowski found females in the wild that first laid eggs at 357, 384, and 291 days. Dr. Pinkowski's work using captive females (which generally nest at younger ages than those in the wild) confirmed this.  Regarding the egg laying of captive females he states:  ".... females will begin laying at an age of about 8 months, and this agrees with with the figures observed by Laskey. It also indicates that a female born on August 1st could be physiologically ready to begin laying by the following April 1, 242 days later." He observed captive females that laid their first eggs at days 209,217, and 238 days, but all were unsuccessful. The average age for those captive females that laid eggs in nests which were successful  averaged 254 days.  John Rogers, Brewerton, NY

Keith Kridler Mt. Pleasant, Texas
When bluebirds fledge from the nestbox I believe they are normally heavier than their parents because they still have baby fat and are not able to exercise fully in a small cavity. Their tail and flight feathers will not be fully formed until about day 35 from their hatch date. (I am guessing here as photo's show their tail to continue to lengthen until about this time.)

To get a height/length of the bluebirds measure down from the top of the entrance hole and draw a horizontal line precisely 6" down from the top of the entrance hole and about 1/2" wide across the front of the nestbox. If the bluebirds tail is on or below this 6" line when they land on the front of the box then they are not midgets:-))

Bluebirds that hatch in August of this year will be able to breed first thing next spring. KK

BEST OF BLUEBIRD_L CLASSIFIEDS HOME | Audubon Society of Omaha | The Bluebird Box | Bluebird FAQs | Search | Contact me

All material was originally posted on the Bluebird_L or Bluebird mailing list, and has been reposted here with slight modifications to make the posts more readable in an HTML format.  In cases in which quoted material has been deleted to save space, this is indicated by an ellipsis (...)

For more information about Bluebird_L, check out http://www.cit.corn.edu/cit-pubs/email/using-lists/index.htm. If you wish to contact the author of a post, you will need to edit the e-mail address, replacing "at" with the "at" symbol (above the number 2 on your keyboard). (This change was made to discourage spammers.)

If you are the author of a posting and would like to see a particular post (or posts) removed from these web pages, please contact me with the web page address, title of post, and date and time of the post(s), and I will remove whatever material you like.  If you have a different opinion from one posted here, you need not contact me, as often I will have a different opinion too. The intent is to try and provide both sides to the issues facing bluebirders, and to do so in an impartial and objective manner.

If you have problems, encounter broken links (unless they are within an e-mail thread, as I do not maintain those links), or have suggestions on how the site can be improved to make it more useful, please contact the Best of Bluebird-L Classifieds webmaster. 

Website design by Chimalis