|Alternative English names: White-bellied
Hawk; Sharp-shinned Hawk (subspecies of); Rufous-thighed Hawk
Alternative scientific names: Accipiter striatus (subspecies
of) Accipiter erythronemius (subspecies of)
Spanish names: Gavilan Pechiblanco
The taxonomy of the White-breasted Hawk has never been fully
sorted out. The AOU currently lump it (and the rest of the
superspecies) as Sharp-shinned Hawk Accipiter striatus, though
acknowledge that this is based on the lack of research done
on most of these forms. All of the field guides that cover
Northern Central America consider the White-breasted hawk
to be a separate species Accipiter chionogaster. Some authors
in the past, eg Dickey and van Rossem (1938) lumped the three
Neotropical forms as Rufous-thighed Hawk Accipiter erythronemius,
but as a separate species distinct from Sharp-shinned Hawk
of North America. This was based on the fact that all of the
Neotropical forms have paler unstreaked underparts (at least
in some variants) and buff to red coloured, unbarred thighs.
Storer (1952) studied skins from Mexico and described a cline
in the paleness of the underparts from north to south Mexico,
with the form madrensis being almost as pale as chionogaster.
I have never seen this form, but a friend of mine, Jesse Fagan,
recently saw one in Oaxaca (southern Mexico) and stated that
it was very similar to chionogaster. I have studied the skins
in the British Museum’s collection at Tring (see attached
photo), where they have many specimens of sharp-shin from
Mexico. None of them show the pale underparts described by
Storer, but the dates (where they exist) indicate that most
were taken in the winter months and so could represent migrant
sharp-shins from further north, rather than resident birds.
The main food of White-breasted Hawks is small to medium sized
birds, though larger species (up to the size of Band-tailed
Pigeon) are also taken. Species identified to date include:
Band-tailed Pigeon, Barred Ant-Shrike; Brown-backed Solitaire,
White-winged Dove, Black-throated Green Warbler, Rufous-naped
Wren, Swainson’s Thrush, Magnolia Warbler and Cley-coloured
Thrush. It has been hard to identify many of the kills directly,
so most of these identifications were made from feathers found
at plucking posts near the nest. I have also seen them eat
a lizard and a bat. This is clearly not atypical as a friend,
Oliver Komar, also observed one trying to catch a lizard.
I have seen birds displaying from the end of December until
early February, though it may well extend beyond these times.
The display flight is similar to that seen in other Accipiters,
with the birds diving downwards on closed wings and then swooping
back up, before diving down again. On April 20th, and therefore
well into the nesting season, I saw a bird circling up very
high then making a slow gliding flight and rocking from side
to side, which had the effect of flashing the white underparts.
I have only seen this once, but it is interesting because
it showed off the one feature that distinguishes the White-breasted
Hawk from the Sharp-shinned Hawk. The individual followed
this flight with a long dive towards a steep ridge, where
it pulled up then circled back up high and flew off into the
The earliest observed nest building was on Feb 7th, when
the nest was already well under construction. This nest was
still a fair way from completion by 20th March. Most nest-building
takes place in the mornings, with both the male and the female
bringing material, but the female doing most of the actual
construction and bringing the larger branches.
The two nest sites, with two nest trees at each site, were
both located on the brow of a steep pine covered ridge. All
four nests were in pine trees (Probably all Pinus oocarpa)
between 20 and 28m from the ground. The nests were constructed
of pine and deciduous twigs (eg Quercus), the latter of which
being taken from small bushes in the open forest under-storey.
The nests were variable in shape; the two in Honduras were
flat platforms on small branching side branches. The other
two were a deeper cone shape located in a fork with the nest
up against the truck. They were all just over 30cm in diameter
and between about 20 to 30 cm in depth. They have a shallow
depression with a loose lining of bark, though this depression
is less evident after the growing chicks have trampled into
more of a flat platform. The nest trees were never the largest
in the vicinity and the nests were located between two-thirds
and three-quarters of the way up the trees.
The four nests studied to date had 2 or 3 eggs. The eggs
are subelliptical in shape; the ground colouration was very
pale bluish white, marked with mostly rusty brown, but sometimes
dark brown, spots and blotches. The markings vary in extent,
even within a clutch, from a few small specs to large blotches
covering around 25% of the surface. The markings are randomly
distributed about the egg. Of five eggs that have been measured,
the wieght averaged 20.8g, the length averaged 38.5mm and
the width averaged 31.3mm
The molt follows a similar pattern to other Accipiters, such
as Sharp-shinned Hawk. Very young chicks had thin white down.
As with other Accipiters, older chicks have a second growth
of down. This was evident in H03 where both chicks had white
down when only a few days old, but two weeks later one had
white down and the other mostly grey coloured down. The bird
with white down was slightly the larger of the two, but they
could not be sexed at this age so it is not evident if this
is a difference between the sexes, or just individual variation.
Females do a suspended moult during incubation; the amount
varying between individuals. They tend to lose most of their
tail feathers and inner primaries, leaving around 4 outer
primaries unmoulted. They also seem to lose most of their
body feathers and tertials, though the extent has been hard
to determine from field observations. No males have been observed
to moult during the nesting time. A couple of skins of males
in the British Museum were showing some moult in August and
September, suggesting that they wait until the chicks have
fully fledged before starting. Presumably, the females complete
their moult at this time as well.
Rubbish dump site with Jason
Known from Biotopo del Quetzal
Also seen at Campamento in Olancho
Known also from La Montañona
Storer, R. W. (1952) Variation in the resident Sharp-shinned
Hawks of Mexico. Condor, 54, 283-9.
Webber, T. and Brown, J. L. (1994) Natural history of the
Unicolored Jay in Chiapas, Mexico. Proc. West. Found. Vert.