Bluebird Update

  Bluebirds at a bird feeder  


Eastern Bluebird 2013 2014
Number of Eggs 531 521
Percent of Hatch Rate 85% 82.53%
Number of Live Young 453 430
Percent of Fledge Rate 88% 90%
Number of Fledged 398 387
Tree Swallow 2013 2014
Number of Eggs 561 530
Percent of Hatch Rate 75% 82.08%
Number of Live Young 418 435
Percent of Fledge Rate 78% 87.59%
Number of Fledged 324 381
House Wren 2013 2014
Number of Eggs –* 42
Percent of Hatch Rate –* 88.10%
Number of Live Young –* 37
Percent of Fledge Rate –* 62.16%
Number of Fledged 49 23
House Sparrow 2013 2014
Number of Eggs 26 43
Percent of Hatch Rate 0 0
Number of Live Young 0 0
Percent of Fledge Rate 0 0
Number of Fledged 0 0
Purple Martin 2013 2014
Number of Eggs –* 47
Percent of Hatch Rate –* 89.36%
Number of Live Young –* 42
Percent of Fledge Rate


Number of Fledged 17 40
*2014 is the first full year of monitoring for these species.

Despite a slow start due to a cool spring, Holden's bluebirds had another great year, fledging 387 new birds.


Tree swallows, taking advantage of the bluebirds' slow start, built nests and laid eggs a bit earlier than normal.  This jumpstart, combine with years of population growth, led to the best year in Holden's history for the number of tree swallows fledged – 381.  


Overall, the weather in 2014 was fairly mild and not terribly stressful to our birds.  We had few very hot days, which can kill eggs and chicks, and little trouble from cold/wet weather, which can limit insects and lead to starvation.  As a result, fledging rates were higher in 2014 than in 2013 – a higher percentage chicks survived and left the nest.  


2014 ranks as the eighth best year on record for number of bluebirds fledged. And the best year for tree swallows. Another bird species, purple martins, is also doing well at Holden.  Nesting structures were installed in 2011 at two locations, Fisherman's Ponds and Hourglass Pond.  The number of martins fledged has increased from two in 2012, to 17 in 2013, to 40 in 2014.  


You'll notice that no house sparrow eggs hatched in either 2013 and 2014.  There's a very good reason for that: we did not allow them to hatch.  House sparrows are non-native, invasive birds that were introduced to the United States more than 100 years ago.  In that time, they spread like wildfire and caused untold death and destruction to our native birds.  House sparrows will attack and kill adult bluebirds (and other species) in order to take over a nest.  They will destroy eggs, kill young, and build their nest on top of the eggs or dead chicks.  So, we remove sparrow eggs (and nests) as a way to manage the sparrow population.  Fifty years of sparrow management has made a difference: in 1965, sparrows occupied 134 nestboxes; in 2014 sparrows made just 10 nest attempts.


Holden’s bluebird program reached a milestone in 2013, having fledged more than 10,000 bluebirds in the history of the program.  2014 represented another milestone: the 50th year of data collection, making this one of the longest-running bluebird programs in the state. Thank you to all the volunteers, past and present, who have helped make this such a successful conservation program.


For more details on the volunteer bluebird monitoring program contact Mike Watson at 440.946.4400 or