Breeding behavior of the laughing falcon (Herpetotheres cachinnans) in southwestern Ecuador and northwestern Peru

Abstract

Though it has received more attention than many other tropical raptors, the Laughing Falcon (Herpetotheres cachinnans) remains a poorly known species. Here we provide data from two Laughing Falcon nests we studied in the Tumbesian region of northwest Peru and southwest Ecuador. We observed the nests for a total of 304 hr. The incubation period was approximately 40 d at one nest. The nestings were observed in one nest in March, in the other in August. During incubation, the female spent the majority (90.1%) of the day on the nest, leaving only to feed on prey delivered by the male. There were no pronounced incubation rhythms, but the female showed a tendency to take breaks between 08:00 and 09:00. The nestling was fed an average of 1.3 times per day, again on food brought entirely by the male. We observed 10 duets between members of pairs that lasted between 3.47 and 10.37 min. Site fidelity and nesting season appeared consistent among years in each nest, but differed between the two nests. The female spent 4.5% of her time while on the nest engaged in behaviors other than incubation, particularly nest maintenance.

Full text

ABSTRACT
Though it has received more attention than many other tropical raptors, the Laughing Falcon
(Herpetotheres cachinnans) remains a poorly known species. Here we provide data from two
Laughing Falcon nests we studied in the Tumbesian region of northwest Peru and southwest
Ecuador. We observed the nests for a total of 304 hr. The incubation period was approximately
40 d at one nest. The nestings were observed in one nest in March, in the other in August.
During incubation, the female spent the majority (90.1%) of the day on the nest, leaving only to
feed on prey delivered by the male. There were no pronounced incubation rhythms, but the
female showed a tendency to take breaks between 08:00 and 09:00. The nestling was fed an
average of 1.3 times per day, again on food brought entirely by the male. We observed 10 duets
between members of pairs that lasted between 3.47 and 10.37 min. Site fidelity and nesting
season appeared consistent among years in each nest, but differed between the two nests. The
female spent 4.5% of her time while on the nest engaged in behaviors other than incubation,
particularly nest maintenance.
Keywords: Ecuador, Herpetotheres cachinnans, Laughing Falcon, nesting, Peru.
RESUMEN
El Halcón Reidor (Herpetotheres cachinnans) ha recibido mas atención que la mayoría de los
otros rapaces tropicales, pero sigue siendo una especie poco conocida. Aquí presentamos datos
sobre dos nidos de H. cachinnans que estudiamos en la región de Tumbes en el noroeste de Perú
y el suroeste de Ecuador. Observamos los nidos durante un total de 304 hr. La incubación en un
nido duró aproximadamente 40 d; un nido tenía pichones en marzo, el otro en agosto. Durante la
incubación, la hembra pasó la mayoría (90.1%) del día en el nido, y salió solamente para
alimentarse de la presa traída por el macho. No observamos ritmos marcados en los períodos de
incubación, pero había una tendencia a salir entre 08:00 y 09:00. El pichón fue alimentado un
promedio de 1.3 veces por día, siempre de presas traídas por el macho. Observamos 10 dúos
que duraron entre 3.47 y 10.37 min. Fidelidad al sitio y a la época de anidación parecía
consistente entre años en cada nido, pero diferente entre los dos nidos. La hembra pasó 4.5% de
su tiempo en el nido haciendo otros comportamientos aparte de la incubación, principalmente
relacionados al mantenimiento del nido.
Palabras clave: anidación, Ecuador, Halcón Reidor, Herpetotheres cachinnans, Perú.
BREEDING BEHAVIOR OF THE LAUGHING FALCON (HERPETOTHERES CACHINNANS)
IN SOUTHWESTERN ECUADOR AND NORTHWESTERN PERU
Comportamiento de anidación del Halcón Reidor (Herpetotheres cachinnans)
en el suroccidente de Ecuador y el noroccidente de Perú
Eliot T. Miller
Harris World Ecology Center, Department of Biology, University of Missouri, St Louis, Missouri and
Yanayacu Biological Station, Cosanga, Napo, Ecuado.
eliotmiller@umsl.edu
Harold F. Greeney
Yanayacu Biological Station, Cosanga, Napo, Ecuador.
revmmoss@yahoo.com
Ursula Valdez
Department of Biology, University of Washington, Seattle, Washington.
uvaldez@u.washington.edu
Ornitología Colombiana No. 10 (2010): 43-50 43

INTRODUCTION
The Laughing Falcon (Herpetotheres cachinnans)
is a widespread but only locally common diurnal
raptor in the Neotropics (Ferguson-Lees & Christie
2001, Fig. 1.). As it occurs at higher densities in
edge and disturbed habitats than in closed forests
(Parker 1991, Enamorado & Orrego 1992), and
across a large geographic area, it might be
presumed to have a secure future. Accordingly, it is
considered a species of Least Concern (BirdLife
International 2010). In some badly fragmented
areas, however, such as western Ecuador (Dodson
& Gentry 1991), the species is considered
uncommon to rare, and perhaps declining
(Ferguson-Lees & Christies 2001, Alava et al.
2002), and its specialized diet may limit its success
in areas with large human populations (Wetmore
1965).
The nest of the Laughing Falcon has been described
from a variety of localities (Wolfe 1954, Mader
1981, Robbins & Wiedenfeld 1982, Parker 1990,
Specht et al. 2008). Nests are generally placed in
somewhat exposed situations, either in an isolated
tree or above the height of the surrounding
vegetation, and are often located in a naturally
occurring cavity or depression, with little to no
material added by the adults (Parker 1990). The
incubation period is reported as 40-42 d in Di
Giacomo (2005), but no details are provided, and
all detailed studies have focused on the nestling
period, which is 50-57 d (Skutch 1960, Robbins &
Wiedenfeld 1982, Parker 1990, Parker 1991,
Enamorado & Orrego 1992, Specht et al. 2008).
The Laughing Falcon feeds primarily on snakes
throughout its range (Skutch 1960, Haverschmidt
1962, Parker 1990, Robinson 1994). This includes
venomous species, such as coral snakes (Micrurus
spp. Howell 1957, Skutch 1960, Wetmore 1965,
Parker 1990, Enamorado & Orrego 1992, DuVal et
al. 2006), at least four genera of pit vipers
(Crotalus, Porthidium, Bothrops, Agkistrodon spp.
(Parker 1990, Enamorado & Orrego 1992, Specht
et al. 2008), and many non-venomous species.
While working in the Tumbesian region of
southwest Ecuador and northwest Peru, we found
two Laughing Falcon nests. The first, which we
studied in Peru in 1992 and 1993, was observed
only during the nestling period. The second, which
we studied in Ecuador in 2006, was found early in
the incubation period. Here we present data from
these two nests to add to our understanding of the
breeding biology of the Laughing Falcon.
METHODS
The first Laughing Falcon nest was located in the
65,000 ha El Angolo Game Reserve, in Piura, Peru
(Fig. 1). The dry forest and thorn scrub in this area
is dominated by species of Malvaceae (Eriotheca
ruizzi, E. discolor) and Fabaceae (Acacia macra-
cantha, Prosopis pallida; Ríos 1989). Annual mean
temperature at the site is 17°C, and rainfall ranges
from 200 to 500 mm (CDC-UNALM 1995). On 19
August 1992 we located a Laughing Falcon nest (=
“El Angolo” nest) that contained a single feathered
Breeding of the Laughing Falcon Miller, Greeney & Valdez
44
Figure 1. A distribution map of Herpetotheres cachinnans,
with El Angolo, Peru and Jorupe, Ecuador, the two study sites,
noted. The distribution data were taken from Ridgely et al.
(2007) and modified slightly in ArcGIS 9.3 by extending the
southern boundary of presence to include the El Angolo nest.

45
nestling. We observed this nest for 84 hr between
this date and 25 August 1992. We returned on 16
August 1993 to find the nest again contained a
single nestling, which we observed for 89 hr
between this date and 26 August 1993. We
conducted these observations with a spotting scope
between 0:500 and 19:30 from two sites located 6
and 25 m from the nest tree. We were able to see
partly into the nest cavity, and base our description
of the nestling period on these observations.
The second Laughing Falcon nest was located in
the Jorupe Reserve, Ecuador (Fig. 1). Vegetation
and rainfall at Jorupe are similar to El Angolo
(Miller et al. 2007). Two park guards located this
nest (= “Jorupe” nest, Fig. 2) and noted the
approximate date on which the egg was laid (1
April 2006). On 8 April we placed a camera ~30 m
away from the nest tree. From 9-22 April,
whenever possible, we filmed the nest from 06:00
to 18:00 (131 hr total). Tapes were transcribed,
digitized, and archived at the Cornell Lab of
Ornithology. These observations were augmented
by ~15 hr of opportunistic study of the pair in the
vicinity of the nest, e.g. watching prey transfers
away from the nest. All of our conclusions about
the incubation period come from the Jorupe nest.
At both nests we documented sex-specific activity
patterns and size, type, and rate of delivery of prey
items. At the Jorupe nest we also noted nest
maintenance behaviors, incubation rhythms, and
quantified the average length of duets and the time
until and length of syncopation. We defined the
beginning of a duet as when the vocalizations
between the female and male moved from quiet,
occasional calls to regular, insistent calls back and
forth between the pair. Syncopation was defined as
a regular call and response, where one individual
called and the other immediately responded,
Ornitología Colombiana No. 10 (2010)
Figure 2. The female Laughing Falcon from the Jorupe nest. The nest can be seen behind and above the epiphytic plants; the
egg is visible in the background. Photo: Murray Cooper.

generating a rhythmic wa-co wa-co.
RESULTS
The El Angolo nest was located ~700 m above sea
level (ASL) in a cavity in a 10 m tall, 56.2 cm
diameter at breast height Eriotheca ruizzi tree
situated on a slight slope and surrounded by other
bombacaceous trees (8-12 m high), thorny shrubs
(2-4 m high), and low herbs and cacti. The nest
opening faced 220° SW and was 5 m above the
ground. The cavity was 36 cm deep, 37 cm wide,
79 cm high, and filled to about 14 cm deep with
organic debris, dry feces and prey remains.
The Jorupe nest (Fig. 2) was located in the lower
hills of the reserve, at 650 m ASL, and placed ~15
m up in a large, isolated Ceiba trichistandra
(Malvaceae, ~30 m tall) that emerged from a thorny
understory into an open canopy of other C.
trichistandra (Fig. 3). The nest was situated in a
depression in the side of the trunk. Epiphytic plants
grew out of the bottom of this depression, creating
a platform on top of which the pair nested. A single
egg was visible and was bronze-colored with large,
chocolate blotches.
We were able to infer the approximate length of the
incubation period. On 9 May 2006 the Jorupe
female was observed incubating. On 12 May a
young nestling was observed in the nest. We
assumed incubation began on 2 April, the day after
the egg was laid. The implied incubation period,
assuming a hatch date of 11 May, was
approximately 40 d.
Nesting of the two pairs that we observed appears
to be fairly temporally consistent among years,
though not between sites. The El Angolo nest
contained a nestling in August in both study years -
1992 and 1993 - as did a nearby nest in 1989
(observed by the authors but not discussed here).
These observations suggest hatching may occur in
El Angolo in July or early August. This is well after
that of the Jorupe nest (11 May). The park guards
again observed the Jorupe female incubating on 1
March 2007.
Sexes of the Laughing Falcon cannot be
distinguished by plumage, and are only slightly
dimorphic in size (Ferguson-Lees & Christie 2001).
None of our study birds were banded, but at both
nests we visually identified a larger individual that
we assumed to be the female. This larger individual
did all the incubation (Jorupe) and nestling care (El
Angolo).
For both nests the male was responsible for all
observed hunting, providing food for both the
female and the nestling. During incubation, the
female spent the majority of her time in the nest
(90.1% of 131 hr filmed). Her incubation rhythms
during this time were irregular (Fig. 4), and the
only obvious patterns that emerged were her
propensity for off bouts between 08:00 and 09:00,
and the long on bouts she endured; in one case she
remained on the nest for 6 hr 57 min. During the
Breeding of the Laughing Falcon Miller, Greeney & Valdez
46
Figure 3. Nest location of Herpetotheres cachinnans in a
natural hollow in a Ceiba trichistandra tree in dry forest of
The Jorupe; the female is incubating (circle). Photo: Murray
Cooper.

47
nestling period the female spent much of the
observation time (96%) perched in 3-4 trees around
the nest, though she occasionally entered the cavity
if the nestling called repeatedly; the male spent
most of the time out of the nest area and we were
only able to observe him from our vantage point for
22 of 173 hr of observation (12.7%).
Though we never observed either nest long after
dark, we did regularly start filming incubation
before dawn and continue filming until after dusk.
From this we infer that the female always spent the
night on the nest during incubation. Similarly, from
our direct observations in the vicinity of the nest
tree in the late afternoon and evening, it appeared
that the male roosted in the nest tree as well. He left
in the early morning and generally returned mid-
morning and again in the afternoon to deliver prey
to the female. For both study pairs, prey was passed
to females off the nest, in the canopy of the nest
tree or of one adjacent to it.
When delivering prey to the incubating female, as
the male neared the nest tree he called loudly,
which alerted the female to his approach. She
would then rise from her position on the egg,
stretch, walk towards the rim of the platform, and
fly into the crown of the nest tree. She also
generally began to call during this time,
occasionally while still perched on the nest rim. A
series of calls followed, which occasionally
developed into a full duet. After the prey was
transferred, the female took it to a different perch to
eat or, during the nestling period, flew to a tree in
front of the nest and waited for 10-15 sec before
entering the cavity to feed the nestling. When we
first began to watch the El Angolo nest, the female
placed small pieces of food in the beak of the 1-2
week-old nestling. After ~5 d of observation
however, she let the young falcon feed by itself
while she remained in the area. After feeding, the
female at the Jorupe nest remained in the area for 5-
35 min before resuming incubation. During these
encounters she consumed the prey and generally
preened and vocalized with the male. The male
often remained in the tree for much longer, on one
occasion at least two hours after the initial prey
transfer.
We directly observed five snakes brought to the
Jorupe nest. These ranged in size from
approximately 50 to 120 cm. Small snakes were
grasped behind the head and carried in the bill.
Larger snakes were also held in this way but, in
addition, the lower portion of the snake was
clutched in the talons. On 2 May 2006, one of the
park guards observed the male deliver a frog.
We observed 18 prey items delivered to the El
Angolo nest. From this we estimate that across the
nestling period, the nestling was fed an average of
1.3 prey items per day (18 items/173 total
observation hr * 12.5 observation hr/d = 1.3 items/
d, range 1-4). Most of the prey items carried to the
nest were medium-sized colubrid and elapid snakes
approximately 50 to 60 cm long, green iguanas
approximately 15 to 30 cm long and, occasionally,
small lizards of the family Teidae. Dietary
composition was not tabulated separately for
nestlings and adults, but that of the nestlings was
similar to that measured during 463 hr of direct
adult observations at the same study site, where
69% of prey items were snakes, 23% were iguanas,
4% were small lizards, and 4% were unidentified (n
Ornitología Colombiana No. 10 (2010)
Figure 4. The incubation rhythms of the
female Laughing Falcon at the Jorupe
nest in southern Ecuador in 2006. Day
of incubation is shown along the left
margin, time of day along the bottom,
and total percentage of that day’s
observation spent incubating along the
right. Gray represents time not filmed,
white represents an off bout, and black
represents an on bout. The figure begins
with day 7 of incubation and continues
through day 21, as this encompasses our
study period. The short incubation bout
at 08:30 on day 21 was due to human
disturbance in the area.

= 71, Valdez 1996).
Ten duets were recorded at the Jorupe nest. All
occurred between 06:23 and 09:10 with one
exception, at 16:46. We rarely observed the birds
after 18:00 and could not determine if duets
occurred in the evening as described (e.g.
Enamorado & Orrego 1992). Duets ranged in
duration from 3.47 to 10.37 min (mean 6.42 ± SD
of 2.49). In eight out of ten duets the pair reached
full syncopation. The time until syncopation ranged
from 0.08 to 3.27 min (mean 1.70 ± SD of 1.52).
The time the pair called in syncopation ranged from
1.93 to 6.65 min (mean 4.28 ± SD of 1.53).
The female was observed to give what may have
been a whisper call. In these cases, though we
could not hear her, we were able to observe that the
female’s bill opened in response to the male calling
from nearby. Also, the pair occasionally continued
vocalizing long after a duet had ended, in some
cases up to 1.5 hr after the female had returned to
the nest. The calls given by the female from the
nest during these times were not always quiet; in
fact, some were quite forceful, accompanied by
head-bobbing, and given in direct response to
queries from the male above. These louder calls
were best classified as “chuckles,” “koahs,” and
“wahs,” sensu Parker (1997).
Though the Jorupe female spent the vast majority of
the incubation period in the nest, on average, 4.5%
of this time (SD = 1.8) was spent engaged in other
activities such as standing (generally immediately
after arriving, before departing, and in response to
perceived threats), preening, picking at the nest and
the surrounding vegetation, repositioning both
herself and the egg, and calling quietly and head-
bobbing. Both sharp and rapid probes (sensu
Greeney 2004) were observed at the Jorupe nest.
Rapid probing was rare, and we more regularly saw
sharp probes, subdued picking, and kneading the
nest with her talons, especially upon arrival.
DISCUSSION
The Laughing Falcon and the genus Micrastur are
members of the Herpetotherinae, a subfamily that
diverged early in the history of the Falconidae
(Griffiths 2004). Our observed incubation period of
~40 d is similar to that of Parker (1997), who
estimated it to be 45 d, and to the 40-42 day period
reported by Di Giacomo (2005). Our value is also
consistent with those of Micrastur: 46 d in M.
semitorquatus (Thorstrom et al. 2000a), 33-35 d in
M. ruficollis (Thorstrom et al. 2000b), and 38-39 d
in M. buckleyi (UV pers. comm.), larger, smaller,
and approximately equal-sized Neotropical forest
raptors, respectively, as compared with the
Laughing Falcon.
Like many other birds in southwest Ecuador
(Marchant 1959, Best et al. 1996), the breeding of
the Laughing Falcon may be tied to the rainy
season. Generally, the Tumbesian region receives
its greatest rainfall in March (Best & Kessler 1995),
and from our limited data it seems that Laughing
Falcons in the Jorupe area nest soon after this
period of heavy rainfall. This pattern is likely
linked with the emergence of large amounts of
suitable prey to provision growing nestlings.
Our observations of snakes up to 120 cm increases
the length of prey known to be taken by this falcon
(Duval et al. 2006). That said, Parker (1990) did
note that Laughing Falcons will attack Boa
constrictor 72 cm in length, and the longest snakes
we observed were thin Leptodeira-like colubrids.
We note that few duets failed to develop into a
syncopated state, and hypothesize that this
component of the duet may be especially important
to these pairs. Further support for this idea comes
from the regularity of hours at which these duets
were given, and the likely importance of duetting to
territorial defense in these specialist predators
(Parker 1997, Hall 2004).
As shown in the incubation rhythms (Fig. 4),
though the female’s off bouts were generally not as
predictable as the few other species for which
comparable data exists (e.g. Greeney et al. 2008),
she did exhibit a propensity for off bouts between
08:00-09:00. It was during these breaks when the
pair often duetted, especially if they had not done
so during an earlier prey transfer in the day. We
suggest that the predictable incubation rhythms in
small insectivores may be related to their need to
regularly feed; the observed lack of predictability in
this study may thus be related to the large food
Breeding of the Laughing Falcon Miller, Greeney & Valdez
48

items consumed by Laughing Falcons (Nagy 1987).
As noted by Greeney (2004), nest probing may help
to remove ectoparasites from the nest. In support of
this idea, the Jorupe female was often seen to
consume small invertebrates after such probing
bouts. Additionally, by depressing the nest material
below the egg, when the female probed the nest the
egg occasionally rolled, and this may have been an
indirect method of accomplishing this.
Parker (1997) noted that successful nests generally
contained nidicolous ant colonies. As we never
climbed to the nests, we are unable to determine
whether our study nests also held ant colonies.
However, at both the Jorupe and El Angolo nests,
regular streams of ants were observed walking
along the trunk and traveling in and out of the
cavity. Wolfe (1954) commented on the stinging
ants present in his presumed nest tree. Such avian-
hymenoptera associations are widespread (Quinn &
Ueta 2008), and future studies of Laughing Falcons
should examine this relationship.
ACKNOWLEDGEMENTS
We thank Rudy Gelis, Leonidas E. Cabrera F. and
Giovanni Cabrera for help in the field. We also
thank Francisco Sornoza and the Jocotoco
Foundation for access to Jorupe, The Peregrine
Fund Research Library, José Hidalgo for assistance
with the map, Murray Cooper for the photo, and the
Loiselle and Blake lab groups, Lloyd Kiff, Russell
Thorstrom, Joan Morrison, and three anonymous
reviewers for help with previous drafts of this
manuscript. Partial funding was provided by the
Population Biology Foundation, John V. and the
late Ruth Ann Moore, Matt Kaplan, the Forestry
Department of the Universidad Nacional Agraria la
Molina and the Lende Simmons Fund. UV wishes
to thank Antonio Tovar, Pedro G. Vásquez,
Mercedes S. Foster, Martha J. Groom and Fiona
Wilkinson. This is publication no. 192 of the
Yanayacu Natural History Research Group.
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Recibido: 12 abril 2010
Aceptado: 28 diciembre 2010
Breeding of the Laughing Falcon Miller, Greeney & Valdez
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