This box was moved to a new location on private property before the nesting season 2011. This is the box in a recent post below featuring the nesting material made of grasses left in the Noel hardware cloth entry-hole guard on this site.
FIRST BROOD FOR SEASON BY CACH: To summarize happenings at this box, the first brood using this box was the Carolina Chickadee (CACH). This chickadee female (at least I think it’s the same female) made two nest cups in the box and laid 2 eggs in each cup. There was ONE hatchling from the 4 eggs. On box checks the sole hatchling appeared to be struggling to survive. I wonder now were there two CACH females fighting to lay eggs in the box and one female was finally chased off by the other and she only incubated her own eggs? I followed the sole hatching grow but with very slow development. It appeared to me the one nestling fledged but all other eggs had disappeared. I cleaned out the box.
SECOND BROOD BY FIRST EABL COUPLE: Within two weeks, a new nest was completed by an EABL–this nest had been built out of grasses. 5 blue eggs were laid within one week after that. All nestlings did well and fledged. My observations of the parents were both were active in caring for their young and always present on my box checks. I cleaned out the box after those baby bluebirds fledged.
THIRD BROOD BY DIFFERENT EABL FEMALE: Within 5 days (!), another EABL female (yes, a different female) had built a pine needle nest and laid ONE WHITE egg so far on my box check. White eggs are rare but do happen. 4-5% of bluebirds will lay white eggs instead of blue ones. These eggs are generally as fertile as the blue eggs. This means it is a different female laying in this box. I am waiting for the completed clutch. Since I think yesterday was the first date of this one laid egg, I will return in 5 days to
see if a clutch of 5 eggs have been laid. If I see 4 eggs, I can assume “yesterday” was the last lay egg date to document in my trail notes.
The best part of monitoring nestboxes, in my opinion, is watching the variety of happenings with all of our native cavity-nesting birds that like to use man-made nestboxes. This is why I always carry two cameras with me on my regular trail checks. It truly is a learning experience. Additionally, this is why we monitors keep detailed trail notes (I think it’s rather fun, actually!)
and I write everything down, such as time of day I am at the box, if the box is in shade or sun, temperatures at box check, other environmental differences such as do I hear or see any of the bluebird parents and are they swooping at me or just watching me
from a distance, are the nestlings struggling and having labored breathing from the heat, does the base of the pole need to be trimmed of taller grasses or weeds, is the stovepipe baffle sturdy or in need of tightening or repair, is the nest material dry, are there any attempts of insects such as wasps, small spider web building, possible ant invasion, etc. I also see different nesting
materials on cavity-nesting species in competition and who wins over a box and how each species wither removes OR incorporate the other species’ nest materials into their own. I have learned the bluebird cannot remove House Wren sticks, so once a house wren wins over the box, a monitor can learn to establish if the sticks are for a real nest for egg laying or if it’s a dummy nest (which once determined, a monitor can remove the sticks). It is illegal to remove an active native bird’s nest, so this is a challenge to determine this. House Wrens are tricky. This bluebird laying the white eggs is indeed a different female. I wish I knew if it was the same male or not. Perhaps something happened to his original mate (killed?) or he decided to pick a new lady to raise another family. Since I’m not a licensed bird bender, I cannot know for sure. My experience and from discussions with other expert luebirders is the couple stay together for the nesting season, then split apart into the mixed flocks in autumn. There are occasions for one reason or another why he look for a new mate to raise a family. OR….perhaps the couple using the box before was finished breeding and a new couple needed a nest box to raise a family.
To learn more about why bluebirds sometimes will lay white eggs, see the Sialis.org website to read up on this interesting topic: http://www.sialis.org/whiteeggs.htm