Observations of Red-headed Falcon Falco chicquera (Aves: Falconiformes: Falconidae) nest at Keraniganj, Dhaka, Bangladesh, with a focus on post-fledging behavior

Author Details: Mohammod Foysal is a young wildlife researcher. He studied on zoology and completed his M.S in Wildlife and Environment Conservation from Jagannath University, Dhaka, Bangladesh. Currently he researching independently some falcon species in Bangladesh and waders specially on Spoon-billed Sandpiper on behalf of Bangladesh Spoon-billed Sandpiper Conservation Project as a Co-investigator of the project.


INTRODUCTION
The Red-headed Falcon Falco chicquera is a resident in tropical Africa, Iran, and the Indian subcontinent (Ferguson-Lees & Christie 2001). Although widely distributed and resident throughout the plains of the subcontinent, it is scarce and local, and probably declining due to habitat degradation (Rasmussen & Anderton 2005;Naoroji 2007). It prefers open habitats, but clumps of leafy trees are used for nesting and roosting (Naoroji 2007).
A few published pieces of information on the study of the breeding ecology of this species in the Indian subcontinent are: Dharmakumarsinhji (1954) on nesting in urban area; Dharap (1974) on nesting in densely populated area, Khan (1978) on ecology and behavior, Gole (1980) on nesting on man-made structure in urban areas, Subramayana (1982;1985) on breeding, hunting and feeding, Foysal (2010) on breeding and Naoroji (2011). Naoroji's (2011) paper on breeding in Gujarat, India, is noteworthy, but awareness of the breeding biology and ecology is still patchy.
This falcon is an uncommon raptor in Bangladesh (Khan 1996(Khan , 2008. According to Naoroji (2007) and Siddiqui et al. (2008) this is a rare and the only known breeding falcon among the 10 species of falcons in Bangladesh. The first study on this falcon in Bangladesh was conducted by Khan (1978) followed by Foysal (2010).
Although nesting on man-made structures in urban and suburban areas has been documented (Gole 1980;V. Prakash pers. comm. in Naoroji 2007;Foysal 2010), little is known of the detailed ecology of the Asian race F. chicquera in the expanding urban areas of South Asia, while the incubation period, nestling period and postfledging dependence period have not been determined for the South Asian race. In this paper I present some observations on the breeding behavior from the onset of nesting to post-fledging on a falcon pair in a suburban area of Dhaka.

Study area and field methods
Fieldwork was carried out at Hasnabad (23 0 40.639N & 90 0 25.490E) a suburb of Keraniganj, Dhaka. Keraniganj is located at the southern edge of Dhaka City, close to the congested old city, isolated by the Buriganga River. While areas to the north and east of the nesting site are densely populated, those to the south and west are more open and rural, with scattered human settlements. A chemical factory, many brick fields and a ship building yard are located eastward of the nesting pylon. While Hasnabad lacks tall trees, many electricity poles and pylons with a power station exist. The heights of poles and pylons are 6-30 m and a communication pylon of ca. 50m, was present and it was on one of these that a nest of Redheaded Falcon was found in March 2009 (Foysal 2010).
The observation began on 12 January 2009 and continued until 26 February 2010, usually once or twice per day, between 0700-0900 hr and/or 1700-1930 hr. Before fledging sometimes one or two day-intervals without observation occurred between watches. Whenever possible, periods of observation were extended. A nest watch was carried out from the ground near the base of the nesting pylon. A pair of 10×42 binoculars was used for scanning.

RESULTS
The study on the breeding behavior of the Redheaded Falcon pair from the onset of breeding to the next breeding of the pair has revealed notable information on incubation, chick rearing, fledging, post-fledging, hunting, feeding, prey species selection, inter-and intra-specific encounters and post breeding behavior that are given in Table 1 (Table 1 shows nesting/breeding chronology and breeding/nesting stages of the pair).

Onset of breeding
On 12 January 2009 a pair of Red-headed Falcons were first observed perched on a ca. 8m high Coconut Palm Cocos nucifera near a highway at the periphery of a human settlement at Keraniganj. From 12 January to 14 February, the pair or a single bird was seen in this tree. The tree was vigorously defended from House Crows (mainly by the male) and the female was observed entering the leaf base of the tree, which presumably contained a nest. The female was observed remaining at the leaf base for more than 15 minutes. After 14 February, the tree was apparently deserted by the pair. Following the flight-line of the male on 02 March, I discovered a nest together with an incubating bird.

Nest
The nest was located 23-24 m above the ground on an electricity pylon nearly a kilometer south-east from the coconut palm where the birds were first observed. The nest was built on a horizontal metal beam where it joined another beam at a 45 0 angle. The nest had probably been constructed recently by a House Crow, and was made mainly of twigs and some wire, and was taken over by the falcon pair.

Incubation
The incubation was done mainly by the female (89%). Only on two occasions (11% n=18) the male was observed incubating. On 05 and 08 March the male was observed settling on the eggs at 12:12 and 07:15, respectively. On both the occasions the male took two minutes to enter the nest, after the female had left the nest. The eggs remained unattended for 10-18 minutes during the feeding, the preening and the exercising of the female. Usually the male offered food to the incubating female by emitting a soft krik..krik …krik….. call and the female left the nest 1-5 minutes later after the initiation of the call. The incubating female was also observed leaving the nest even when a call was not initiated. The female was not vocal. On only one occasion (18 March) the female emitted a call just before entering the nest. On 11 March the male moved close to nest with partly eaten prey accompanied by a soft krik…..krik….krik…call at 07:15, 07:19 and 07:25 respectively. But the female did not leave the nest. After a hunt the male cached the prey. During the period when the eggs were not attended to, the female's activity included feeding (most commonly), preening, exercising (random wing flaps accompanied by moving on the perch) and territorial aggression. While the female incubated the eggs, the male falcon sometimes remained absent (presumed to be foraging far from the nesting pylon) from the nesting pylon. The male remained absent from the nesting pylon for 10-35 minutes. Clutch size was unknown. Perhaps the eggs were hatched on 23 March. This was confirmed when the female was observed bringing partly eaten prey to the nest for the first time, and continued doing the same on subsequent days (Images 1 & 2).

Brooding
The female alone carried out all the brooding. Brooding discontinued 13 days after hatching. Brooding was completely suspended when the young were 29 days old. Hatchlings remained unattended for 6-17 minutes during the female's feeding out side of the nest. The female first moved away (ca. 100m) from the nestlings with the male 13 days after hatching.

Prey species
The majority of the prey species were small birds. Prey remains suggest that the falcons hunted almost exclusively on House Sparrows Passer domesticus, but occasionally took Pipistrellus bats (n=3, presumed more).

Foraging, hunting and caching
During incubation the male foraged far from the nesting site. On one occasion (late incubation period, on 20 March) the male chased a House Sparrow in the vicinity of the nest. A radius of ca. 150m was used for bat hunting.
During incubation the male hunted far from the nest site, away from observation. After hatching the male increasingly hunted in the vicinity of the nest. The female resumed hunting 18 days after hatching. A total of 32 hunts were recorded from hatching until fledging. The male hunted 78% and the female 22%. A few hunting attempts were made by the male and the female together but all of these were unsuccessful (Fig. 1). The hunting frequency was highest in the morning. For example, on 12 April (20 days after hatching) four hunts (all small birds) were recorded in less than one hour (07:07-08:02).
Prey was cached on the nesting pylon on various metal beams, always above the nest platform, and sometimes openly on a beam.

Feeding the nestlings
The feeding frequency was at its highest in the morning. For example, on one morning (20 days after hatching) four feeding visits occurred in less than one hour with the fourth delivery withdrawn immediately by the female. As nestlings got older the feeding visits increased and then somewhat decreased during the prefledging period (Fig. 2). After hatching until 5 April the feeding duration could not be determined because of constant brooding and less visibility from the ground. However after that, the feeding duration was 1-10 minutes, averaged at 5 min per visit (n=11).

Roosting of parents
The male always roosted away from the nesting pylon. From the pre-fledging period onwards the female also roosted away from the nesting pylon. Most of the time they moved eastward from the nesting pylon either together (16%) or separately (84%) n=19. Where the birds ended up roosting was difficult to estimate. However, on one occasion an adult was observed roosting on an electricity pylon (ca. 30m high) about 500m westward from the nesting pylon.    Pre-fledging From 22 April onwards, when the chicks were estimated to be 30 days old, wing flapping and stretching by the young increased significantly. When the parents arrived, the chicks begged, but the parents didn't respond as much as they had previously. The duration of feeding by the female was now reduced to two minutes (n=2).

Fledging
On 29 April, at the age of 37 days, two chicks fledged while the third chick fledged on 4 May (5 days after the two chicks fledged). On 29 April, one of the fledglings roosted 2m under the nest beam. Another remained ca. 2m above ground on the beam, frequently trying to climb up the slippery metal beam, but failing. At last at 18:43 this fledgling flew ca. 40m and landed on a 2m high coconut palm and roosted there. The next morning this chick was found in the nest. On April 30, the female fed (n=3) the two chicks that remained in the nest; the other chick remained 2m under the nest and did not get fed, despite its vociferous begging.

Post-fledging Feeding by adults and prey transfers
During the post-fledging period, the female usually brought prey to the nest, both hunted by herself or given to her by the male, and then fed the fledglings at the nest. From 14 May, the parents began to only deliver the prey, rather than tearing it up for the fledglings and the last prey was delivered to the nest on 15 May, 16 days after fledging. After 7 June, 39 days post-fledging, prey was no longer delivered to the young (Fig. 3), and thereafter they followed an adult, making begging calls-the last begging call was heard on 13 July, 75 days after fledging. From the observations, it appeared that from 24 days after fledging onwards the fledglings were cared for by a single adult, whose sex was not determined, with the partner adult sometimes sighted c. 600m away.
The siblings were competitive; on 18 May 2009, when one fledgling snatched prey from the adult's talon, the others tried to pilfer it, making begging calls. The fledgling with the food avoided its competitor siblings by making a short flight. On 1 June 2009, one fledgling followed another that had food about 200m away from the nest site. These attempts at thievery were not successful. Only on one occasion 21 days after fledging did a fledgling successfully pilfer food from a sibling.
As they got older, the fledglings approached the adult and grabbed food, rather than being given it. Their behavior became more and more aggressive, for example, on 31 May, some 32 days after fledging, on the approach of the adult with prey, all three fledglings left the nest site and about 50m away one snatched the prey from the adult in midair. The other two siblings grappled with it and all three fell, disengaging only just before hitting the ground.
On two occasions prey fell to the ground from the fledglings during feeding. On both occasion the fledglings stooped at once but failed to retrieve the prey, (one time an Oriental Magpie Robin Copsychus saularis drove the fledglings away).

Nest site defense
Throughout the nesting period the adults were aggressive towards House Crows, Large-billed Crow Corvus macrorhynchus, Black Kite Milvus migrans, Peregrine Falcon Falco peregrinus calidus, Eurasian Hobby Falco subbuteo, and conspecifics, near the nest site. Once during incubation, the female directly joined the male to help drive off a Peregrine Falcon passing close-by. During the nestling period, the female was once observed chasing an intruding male Red-headed Falcon between the beams of the nesting pylon. Her mate then came and vigorously drove the intruder off, making a loud, angry,

Subsequent use of nest
After fledging the nest was used for feeding (51.11%), resting (35.35%) and perching (13.33%, n=45). The nest was used as a food delivery platform by the adults up to 15 days after fledging, thereafter the nest was used only by the fledglings until 11 August, the last observation of the use of the nest. One fledgling was observed resting (perhaps laying in the nest) at the nest for 37 minutes. Juveniles (two together) were last seen on 19 August at the nesting pylon and all the three were seen for the last time on 5 August.

Resightings of parents
The adults started frequenting their old nest site after August. Before they resumed breeding, the adults were sighted 42 times. They were sighted 33 times at the nesting pylon, and the remaining nine times they were sighted in a radius of ca. 400m from the nesting pylon. During this period, their main activity appeared to be hunting and feeding. Others activities were vocalizing, mobbing crows and exercising. During feeding House Crows approached very close to the falcons and often tended to mob them, and occasionally did mob them. The falcons were observed to be not as aggressive as they were during breeding time. On a few occasions (n=5) 3-4 falcons were sighted (presumed juvenile entered natal territory) in the natal territory, and on all occasions the parents were aggressive towards conspecific intruders.

Adults resumed breeding
From 25 December onwards the pair was once again highly aggressive towards crows, vigorously defending a ca. 50m long communication pylon about 200m eastward from the previous nesting pylon. On 29 December mating occurred at 08:25 at the previous nesting pylon (where the three chicks were fledged). Eventually on 26 February 2010, the pair was observed to be incubating again on a third electricity pylon ca. 28m (the highest nest recorded ever for this species) above the ground 630m away from the original nesting pylon.

Nesting
The Red-headed Falcon nests on trees and the nesting height varies from 4-14 m (Naoroji 2007). It prefers large trees where large trees are available, a nest was recorded on a 24m high tree (Subramanya 1982). In 1978 four nests located in Bangladesh were in trees. Three nests out of four were located in Dhaka City (Khan 1978). In the recent past, two nests of different pairs in different districts in Bangladesh were recorded on man-made structures (Foysal 2010).
Nesting on an electricity pylon, as recorded in this study and in the recent past, seems to be a response by Red-headed Falcon to the shortage of large trees and suggests a hitherto little-appreciated ecological flexibility that may help this species survive in increasingly urbanized landscapes.

Incubation
The incubation period has not been previously recorded for the Indian sub continental race (Naoroji 2007). The average incubation period for the African race is 33 days (range 32-35 days; Osborne 1981). Naoroji (2007) mentioned that the Indian race usually laid eggs by end February to early march. The nest that was discovered on 2 March was in incubating condition and the hatching occurred on 23 March. Given that the incubation is at least three weeks in comparison with the African race and the usual egg-laying time of the Indian race, the incubation period could be estimated as a minimum of four weeks, although the days that the eggs were laid are not known for sure.