2016 Tejon Ranch
Breeding Bird Blitz
Ellery Mayence, Tejon
Ranch Conservancy Senior Ecologist
On June 4th, 2016,
Tejon Ranch Conservancy staff and a suite of keen birding enthusiasts (three
teams in total) branched out in different directions across Tejon Ranch,
spending eight hours per team censusing all birds heard and/or seen. One team targeted portions of the San Joaquin
Valley, while the other two canvased the Antelope Valley (East and West). With conditions being warm, sunny, and
generally agreeable for bird watching, a total of 2533 birds were observed
(Figure 1). The greatest number of birds
was observed in the Western Antelope Valley grasslands and associated riparian and
oak woodland habitat (1076), followed by similar habitat in the San Joaquin
Valley (836), and the Eastern Antelope Valley (621), where observers targeted
Joshua tree woodland, higher elevation scrub oak and chaparral vegetation, and ultimately
montane mixed conifer forest. A
different pattern was observed when the total number of species is considered,
with the San Joaquin exhibiting the greatest number of species (55), followed
by the West Antelope Valley (44) and the East Antelope Valley (40).
Figure 1. Total number of a)
birds and b) bird species observed by region of Tejon Ranch as part of the 2016
Breeding Bird Blitz.
A total of 70 species were
observed by the three teams, with more than 100 individuals observed for five
species (horned lark, European starling, mourning dove, tricolored blackbird,
and acorn woodpecker), and fewer than 10 individuals observed for 37 species
(Figure 2). Of the 70 species observed,
69 are native to the region, with the one non-native being the European
starling.
Figure 2. Number of birds
observed by species for the 39 most commonly encountered species. Five or fewer individuals were observed for
the remaining 31 species including: great horned owl, hairy woodpecker,
Stellar’s jay, tree swallow, Bewick’s wren, Cooper’s hawk, barn owl, northern
flicker, black phoebe, northern mockingbird, purple finch, California condor,
greater roadrunner, spotted towhee, western tanager, Scott’s oriole, mallard
duck, turkey vulture, prairie falcon, mountain quail, Pacific-slope flycatcher,
wrentit, yellow warbler, great-tailed grackle, killdeer, downy woodpecker,
Say’s phoebe, ruby-crowned kinglet, Swainson’s thrush, American robin, and
American goldfinch.
With respect to the five most
encountered species, a few conclusions can be drawn. It should not come as a surprise that a large
number of horned larks were observed, as Tejon Ranch supports more than 100,000
acres of grassland habitat, horned larks are obligate grassland species, and
two of the teams spent a considerable amount of their survey time traversing
through grassland habitat. European starlings,
much like acorn woodpeckers, are cavity nesters and the large number of mature
valley oaks on Tejon Ranch provide ideal nesting habitat for such species. Oak woodland is the second most dominant
habitat type on the ranch and two teams dedicated a large proportion of their
survey time to oak woodland – so high tallies for these two species was
expected. Mourning doves, to a large
degree, forage in grassland and roost in woodland, so when the amount of these
two habitat types is combined, this species’ habitat requirements are well
supported on the ranch (and it was frequently observed). However, when it comes to the tricolored
blackbird, neither grassland nor oak woodland is necessarily required nesting habitat,
so why were so many observed? Their
presence and the approximately 200 observations made during the survey is
primarily a result of an 1/8 of an acre cattail-filled stock pond in the West
Antelope Valley portion of the survey.
Interestingly, this same stock pond is also where the majority of the
red winged and Brewer’s blackbirds and great-tailed grackles were observed.
Though none were observed as part
of the official Breeding Bird Blitz, purple martin enthusiasts can rest assured
by the fact that numerous breeding pairs (and colonies) have been observed on
the ranch this year. Tejon Ranch
Conservancy will continue to search for and observe purple martins until early
July to better understand the condition of their preferred and/or required
habitat, nesting site preferences and other behavioral attributes.
The Breeding Bird Blitz was
conducted at a time when many bird species are establishing nest sites, incubating
eggs, or feeding chicks yet to fledge.
As stated before, with grassland being the dominant vegetation type on
Tejon Ranch, it is not uncommon to encounter ground nesting birds (Figure 3) as
one peruses grassland habitat (with not all nests being those of obligate
ground nesting species). When a bird is
flushed from grassy habitat during breeding season, spend time looking because
a nest is often nearby.
Figure 3. Shown (left to
right) are nests of horned lark, mourning dove, and lark sparrow, all found in
grassland habitat of Tejon Ranch in May and June of 2016.
As with previous avifauna
surveys, the 2016 Breeding Bird Blitz was successful, fun and informative. All participants enjoyed their time afield
and are eagerly looking forward to their next opportunity to take part in
similar Tejon Ranch Conservancy-based activities. Please consider monitoring Tejon Ranch
Conservancy’s website and social media pages for news on membership, upcoming
events and outing opportunities.
