Observations on the ecology of Cliff Swallows (Hirundo
pyprrhonota)
Patrick Stadille and students of 6th grade science class
Gymnasium, Carmel Middle School,Carmel, MontereyCounty, CA
Abstract: Cliff Swallows nest in a small colony of around 100 pairs in mud nests under
the eves of primarily the south facing wall of the CMS gym. They gather the mud form
adjacent mud puddles for nests which they construct over a two-week period starting in
mid April. They fill an important niche as insect controllers. They are pretty and active
and useful for students doing scientific field experiments on a dynamic and easily viewed
vertebrate. They also illustrate how man can share his home with nature. The problems of
feces and mud seem manageable and do not warrant exclusion of these animals. Further
observations over the remainder of the school year would be instructive.
Introduction. The Cliff Swallow is a common breeding bird at Carmel Middle School
(CMS). These birds winter in South America and return each year in the spring to breed.
The Cliff Swallow is identified by its peach colored rump and an unforked tail. It has a
white strip above the stubby bill, a dark crown, and a chestnut throat that extends around
the sides of the neck. Fast and highly maneuverable flyers, these birds have dark, narrow
wings with primaries that extend past the tail. Cliff Swallows are colonial and have
benefited from human buildings as they are often found in great numbers nesting under
bridges and the eves of buildings. They construct a gourd-shaped mud nest out of
hundreds of small pellets of mud that they collect from nearby mud puddles over a
sequence of many daily trips. Other swallows at CMS include Barn, Tree, and VioletGreen. Cliff Swallows also build mud nests while the others nest in tree cavities.
Cliff Swallows are a joy to others and an annoyance to others. Their feces and mud
droplets under their nests can be a nuisance and there has been discussion of health risks
to humans from potential pathogens in their dried feces. On the other hand, these birds
likely fill a critical niche in the food chain by controlling the population of flying insects.
Many people enjoy their color, behavior, and the idea of sharing the building and lands
with wildlife. In years past, the CUSD has attempted to discourage nesting by putting up
spikes and knocking down old nests. Unverified stories exist of district personal knocking
down active nests. This is prohibited by the Migratory Bird Act.
The point of this study was to record observations on the ecology and effects of Cliff
Swallow nesting in order to design effective management plans that will facilitate
peaceful coexistence between man and swallow at CMS.
Materials and Methods. Observations were taken at the CMS gym and adjacent
grounds. Approximately two hours total of observing was taken over a 3 day period on
April 30th, May 1st, and May 4th during the late morning from 10:00 am to 12:15 pm. The
weather was unsettled with periods of sprinkles, wind, and clear skies. Temperatures
ranged from 50-70 degrees Fahrenheit. Swallows were observed using binoculars and
data recorded in field notes. The birds were observed from various distances and our
presence did not seem to cause a change in normal behavior. Direct counting surveys of
nest shape to date, number, and location around the gym were taken. Brief observations
were made as to the amount of feces and mud contamination existed around the area.
General behavioral notes were taken.
Results. Behavior: The Cliff Swallow has a high pitched crinkly-chirp of a call. They did
not seem to be alarmed at our presence, even when we were close, looking up at nests.
Occasional mass fly-outs were observed but did not seem to be due to human
disturbance. They did not react to a PE whistle. No cases of diving at us were recorded.
The birds would fly back and forth to get mud from the ground for their nests. There were
three mud spots within 50 meters of the gym. One was on a lawn while the other two
were on bare soil near the softball snack bar. Often in large flocks, they would congregate
at small, shallow mud puddles to gather mud. Dipping down with their beak while
perched on the ground, their wings were extended vertically and moved with a rapid
fluttery motion, presumably to keep clean and dry. Upon returning to the unfinished nest,
the other mate would leave the nest while the other added its mud supply to the nest.
They appeared to switch off when the other returned with more mud. Besides nest
building the birds were observed flying and feeding in the sky. They seemed to feed
higher in the sky when compared to the low flying runs of the Barn Swallow who often
strafe the large expanses of grass. On May 1, no swallows were observed at the site.
None. We were there for at least 40 minutes, counting nests, and no birds were seen.
Later in the day they were spotted and there were hundreds back flying and at the nests
on Monday, May 4th.
Cup-shaped nest.
Nests: The swallows arrived at CMS over a week-long period from April 11th to April
17th. Nests at various stages of construction were observed. Four categories were
established and counted. They were: Flattish, Bowl, Urn, and Complete. (See sketches) A
completed nest is about 6 inches in diameter. The opening is about 1.5 inches in diameter.
(See graph for numbers of shapes as of May 4th.) An estimate of between 100-105 nests
were counted around the gym perimeter. The south side had the most by far with around
90 nests seen. About 70 of these were concentrated on the left side of the south wall as
one faces it. 15 were seen scattered on the west facing wall with none on the north and
east facing walls.
Stages of Swallow Nests on May 4th,
2009
35
# observed
30
25
20
15
Series1
10
5
0
Flat
Bowl
Urn
Gourd
Shape
Waste: The south-facing walls were flecked with white, twig-like fecal pellets
of 1 inch in length. The number would require cleaning of the walls but was not
particularly noticeable or unsightly. The amount of dirt on the ground under the nests did
not attract much notice or concern at this time. The majority of the nests were near and
above the main entrance to the PE classroom. No problems between birds and students
were observed during when there was student activity at the door.
Discussion: The Swallows population seems healthy and thriving at CMS. The wire and
plastic materials to deter nesting form spring 2008 had been removed, probably due to
functional failure or to the possibility that they helped the birds build nests. A behavioral
or health hazard does not seem to be a problem at this time. Research was spent more on
bird ecology and not enough on quantifying fecal and mud contamination. This needs to
be observed more carefully and throughout the breeding season to see if this grows to be
an actual problem by the end of the school year. If problems occur, solutions could be
poop and dirt awnings, rerouting of students into the room via the west wall doors, and
occasional clean-up patrols of walls, the ground, and drinking fountains. These birds at
this time seem to be completely harmless and should be appreciated for their bug
catching services and beauty
Acknowledgments. I would like to thank my science and nature study classes for their
enthusiasm and ideas with this project. Many had good suggestions and observations
about the problem, solutions, and the bird’s ecology.
Literature Cited: Griggs, Jack L., All the Backyards birds, Harper Perennial, 1998
Roberson and Tenney, Atlas of the Breeding Birds of Monterey County,
Monterey Peninsula Audubon Society,1993.