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Thursday, May 28, 2015

Breeding Bird Blitz, by Dr. Phoebe Prather, Senior Biologist




 (photo courtesy of Chuck Noble)

The Tejon Ranch Conservancy is dedicated to the citizen science movement that was pioneered by Audubon more than a century ago.  We have two long-running annual citizen science bird counts that we conduct on Tejon Ranch, the Christmas Bird Count and the Breeding Bird Blitz.  The Christmas Bird Count provides information on bird species wintering on Tejon Ranch, whereas the Breeding Bird Blitz is intended to provide information on breeding species, although we often see many migrants as well.  The Conservancy’s Breeding Bird Blitz is conducted during the late spring in mid to late May.  We use the same 15-mile diameter count circle established for the Christmas Bird Count.  This allows us to collect data in the same locations throughout the year.  Teams are sent to both the San Joaquin Valley and Antelope Valley sides of the Ranch.  Both counts provide vital information about bird populations and trends during the winter and breeding seasons.     

     Photo 1:  Adult long-eared owl captured through the binoculars of our Conservation 
Science Director, Dr. Mike White.


The inaugural Breeding Bird Blitz was conducted in 2009 and it has been conducted every year since.  We counted 112 species that first year (Table 1).  Even though we have never reached that magic number of 112 again, we have continued to add new species to our overall Breeding Bird Blitz species list (Table 2).  Some of these species have also been new to our overall Tejon Ranch bird species list.  Since 2009 we have detected a total of 171 species during the Breeding Bird Blitz.  Please visit our website to view the species lists for each year the count has been conducted.

         Table 1.  Total number of species counted each year during the Tejon Ranch 
Conservancy Breeding Bird Blitz.

Table 2.  Number of species new to the Breeding Bird Blitz species list for each count year.


As our dataset increases each year, we can begin to pull out patterns from the data.  We are beginning to see that in the spring we often find more species in the canyons of the Antelope Valley, rather than on the San Joaquin Valley side of the Ranch (Table 3).  This is an expected trend as both spring migrants and breeding birds are coming from the south and funneling into the resource rich canyons after crossing the desert.  Spring migrants feed and rest before making their way over the Tehachapi Mountains and continuing northward to their breeding grounds.  After refueling in the desert canyons it is easy for birds to zoom over the mountains without needing to settle into the canyons on the San Joaquin Valley side of the Ranch.  Breeding birds find in these canyons the resources they need to settle in and establish territories to nest.  But even though these trends are expected, it is exciting to see them displayed in the data, validating both our hypotheses and the importance of these canyons for both migrating and breeding birds.


          Table 3.  The number of bird species observed during the Breeding Bird Blitz in the 
Antelope Valley versus the San Joaquin Valley.


We conducted our 7th Breeding Bird Blitz on May 16.  Thirteen volunteers joined us for a beautiful day of birding.  Three teams tallied a total of 99 species, adding 4 new species to the overall Breeding Bird Blitz species list.  New species included: long-eared owl, Western screech-owl, Virginia’s warbler, and black-throated sparrow.  Owl families were the theme of the day as one team watched a nesting pair of adult long-eared owls and their two fledgling owlets, and observed an adult burrowing owl feeding a chick.  Another team observed a group of the Sage Sparrows (Mojave race) in a location where we have never seen them before.  The team found it interesting that the sparrows were in a group, rather than separated into breeding pairs.  Perhaps they were a group that was just passing through, on their way to other breeding grounds.  Virginia’s Warbler was just added to the Ranch bird species list the weekend before the Breeding Bird Blitz.  It is simple observations such as these that make birding such a fun activity.  What are these birds up to?  Why have we only just found the Virginia’s warbler?  Do they often pass through undetected or have a few strayed off path this year?  Do the long-eared owls always nest in this spot and we have only just stumbled upon them this year?  Are the sage sparrows starting to breed on the Ranch or are they passing through on their way to some other far off place?  So much mystery is encompassed in such small beings.  Let’s keep questioning and learning!



Photo 2:  Adult long-eared owl and one of its owlets (photos courtesy of Chris Gardner).