NestlingsDead Bluebird Nestlings

Dead Bluebird Nestlings

In 2007, Eastern bluebirds had a brood in a NABS box (Box #B) at a trail I have at a closed landfill. Presumably this is a second brood for a pair that had a successful first nesting in this area, but in a different nestbox (Box #A). Tree Swallows successfully raised a brood in Box B earlier in the season.

Closed Landfill layout.
Box B is located in the Closed Landfill area to the West, near the end of the dirt road.

The first bluebird egg was laid on 6/27/07. A total of 5 eggs were laid. Two eggs had hatched by 7/14. On 7/21, there were three young, but one was dead (on day 8, counting hatch day as day 1). There were a number of engorged blow fly larvae under the nest. The remaining two live young looked listless, their heads seemed small, and their lower abdomens looked distended, and the area around the anus was yellowish and looked kind of swollen. On 7/24 I returned to do a nest change, and one more nestling was dead (day 11). The abdomen looked flaccid. The remaining nestling was listless. I fed it several mealworms which it swallowed. It did not defecate afterwards. Both parents were in the area.

Trail History: This box is on a trail at a closed landfill in NE CT. The grass is mowed once a year, and there are lots of insects in the area (deer flies, grasshoppers, butterflies etc.) No pesticides are used. The grassy area where the boxes are is surrounded by woods on 3 sides, with an active transfer station down below and a residential area beyond the transfer station. Box B is kind of near a methane vent, but the landfill is no longer gassing much at all, as it has been closed for some time.

Box B has been in place for 3 years. See trail logs from 2005, 2006 and 2007, and description of trail. All boxes are spaced 100 yards apart, except for 2 pairs.

  • In 2004, there were only 2 boxes at the closed landfill, both of which were used successfully by Tree Swallows, with no losses.
  • In 2005, 11 boxes were added, including Box B. A total of 52 TRES eggs were laid, of which about 31 fledged. 15 Bluebird eggs were laid, of which 8 fledge. Four Tree Swallow nestlings died in Box B – small, but fully feathered, with messy butts. I had other TRES losses that year in other boxes: a dead adult female on eggs in Box E (found 5/22), 1 dead nestling in Box F (found 7/2), 1-2 dead in Box G (after 7/2), and 4 dead in Box J (found 7/2 and 7/9). I was mystified by the losses, which were not seen on my other trail that year and wrote a web page on possible causes of dead TRES found in nestboxes.
  • On this trail on 7/9/05, I also had problems in Box L, which is hundreds of yards away. Eastern Bluebirds laid the first egg on 4/22. On 5/22, there were four babies, but the nest was wet – the weather had been awful and the box had turned into the prevailing winds. I did a nest change. On 5/29, all four were dead. TRES attempted to use the box next. Four young hatched around 7/2. On 7/9, 3 were dead. The fourth appeared to have fledged successfully. After nestings, all boxes were cleaned out but not disinfected.
  • In 2006, 3 out of 4 Tree Swallow young (hatched around 6/2, found dead on 6/24) also died in Box B. Three TRES nestlings died in Box G, found on 8/5 (still pin feathers). There were no other losses, so I thought the problems in 2005 might have been weather related. After nestings, all boxes were cleaned out but not disinfected.
  • 2007 is the first year Box B has been used by bluebirds. I changed the direction the hole faced to E. TRES had a successful brood of four in the box which fledged by 6/16. I have not found any other dead nestlings in boxes on this trail in 2007.
  • Unrelated? In the bluebird box where there were losses in 2005, there were House Sparrows around (they were trapped and euthanized.) In 2007, House Sparrows (which were also trapped and euathanized) kicked the bluebirds out of box 18, so the bluebirds apparently moved over to box B for the second brood, which is where the losses occurred.


The lower abdomen looks bloated/swollen to me.

See trail logs from 2005, 2006 and 2007


Notice how round the lower abdomen is. The area around the cloaca looks yellow and distended to me. The head looks kind of small.

The eyes look kind of slitty, almost like the bird is too tired to open them all the way. But the eyes are generally just opening up on days 8-11.


Keith Kridler noted that the pin feathers look odd for a bird of this age. They look dried up and small.

See photo of other nestlings on day 8

Perhaps there is a diet/internal parasite problem?

UPDATE: After the death of two of the three nestlings and a nest change, I went back to check on 7/27, and the remaining nestling was still alive, but looked small, head small. Feathers are developing, but don’t look quite right.


As of 7/29, the remaining nestling was still alive. It looks a little ratty. Head size looks normal, abdomen looks normal.

Hatch day 7/14 – counting Hatch day as 1, this nestling is 15 days old. Appears to be a male.


Somewhere over the rainbow
Bluebirds fly.
– from “Somewhere Over the Rainbow,” lyrics by E.Y. Harburg


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