Notes on nesting behavior of Yellow-footed Green Pigeon Treron phoenicopterus ( Latham , 1790 ) in Aligarh Muslim University campus and its surroundings , Uttar Pradesh , India

The nesting behavior of the Yellow-footed Green Pigeon Treron phoenicopterus was observed during its breeding season in 2021 in an urban region encompassing the Aligarh Muslim University Campus and the surrounding areas. Data were collected by searching nests in the study area. The breeding season for the species in the study sites begins in March and re-nesting is attempted even in July. A total of 31 nests were found on 24 trees belonging to eight species. The analysis of nest site characteristics revealed that Millingtonia hortensis, Azadirachta indica, and Dalbergia sissoo were the most important nest tree species, accounting for 69% of the identified nests during the study period. These findings contribute to our understanding of the nesting behavior of the Yellow-footed Green Pigeon in an urban environment and have implications for its conservation and management.


INTRODUCTION
The Columbidae family is one of the world's most threatened families. Despite its widespread distribution, the family, which contains pigeons and doves worldwide has received little conservation attention; is considered to have 369 species, 16 of whom are extinct, and one is extinct in the wild (the Socorro Dove Zenaida graysoni) (Birdlife International 2020). Thirty-three species of Columbidae have a distribution in India. It is most likely because it is one of a group of birds threatened by human persecution, habitat degradation, and introduced predators (Owens & Bennett 2000).
India has an incredible diversity of Columbiformes, inhabiting 33 species, including fruit pigeons (Ali & Ripley 1987;Grimmett et al. 2016). Frugivorous birds are the key functional species, performing valuable seed dispersal services and regeneration and their decline or local extinction may have severe consequences for the functioning of an ecosystem (McConkey & Drake 2002). Yellow-footed Green Pigeon is frugivorous species and is a common resident species in Aligarh district in Uttar Pradesh, where no studies have been carried out on its status, distribution, or ecology. As a result, we planned to investigate the Yellow-footed Green Pigeon nesting ecology in this area. It breeds in the Aligarh Muslim University campus and adjoining areas regularly, and the Indian Jungle Crow Corvus macrorhynchos and House Crow Corvus splendens prey on their clutches and nestlings. A few studies on Columbidae are by Bhattacharya (1994) on morphological adaptations, Somasundaram (2006) and Devi (2012) on the ecology of Nilgiri Wood Pigeon and Yellow-footed Green Pigeon, respectively, and Kour (2016) on eco-biology of some species from Jammu. Therefore, the present study was conducted to present preliminary data on the nesting behavior of Yellow-footed Green Pigeons in an urban region.

Study Area
Aligarh Muslim University is in Aligarh district in Uttar Pradesh, India, in the Ganga-Yamuna doab region. It is located at the northernmost part of the Agra division, stretching from 27.4833 0 N to 28.0166 0 N latitude and 77.4833 0 E to 78.6666 0 E longitude (Image 1). The district covers an area of 3,650 km 2 and is 130 km from Delhi. The flora in the area is dry deciduous with mostly deciduous trees in most areas. The locations of the nest and random plots at both the study sites, i.e., AMU campus (NC i & RC i ) and Aligarh Fort (NQ i & RQ i ) are shown in Image 2.
In central Ganga Plain, the interfluvial stretch of the Ganga and Yamuna passes through Aligarh district. The methodology adopted by Devi (2012) aimed to understand the characteristics of the nesting sites and the factors influencing nesting site selection. To quantify the nesting environment, the methods outlined by James & Shugart (1970), subsequently refined by Mudappa & Kannan (1997), were employed. Data on nesting trees and nesting environment factors were collected and quantified. In order to detect nests of Yellow-footed Green Pigeons in the beginning of their nesting season, we largely depended on their behavioral cues such as collecting nesting material. During the mating season of Yellow-footed Green Pigeons, nest searches were conducted in the study region, and observations on nest trees and nest-site characteristics were made, following the methods used in previous studies (Gokula 2001;Devi & Saikia 2012). To ensure minimal disturbance to the nesting birds, all observations of their nesting activities were conducted from a safe distance, thus preserving the natural nesting behavior of the Yellow-footed Green Pigeon.
Observations of its nesting sites and nest site characteristics were undertaken from 10 March to 13 July 2021, when the final fledglings of active nests fledged. Once an individual or pair was sighted gathering twigs from the trees or constructing a nest, they were followed using binoculars or a camera and their nesting activities were recorded daily from 0630 h to 1130 h. A comprehensive dataset was obtained by closely observing selected nests, while additional nests were also monitored to determine the overall nesting success and gather supplementary data.
Adult birds undertaking breeding activities such as nest construction, incubation, and feeding the young in or near the nest indicated the presence of an active nest. A circular plot with a radius of 10 m was set up around each nesting tree to measure nest-site selection along with random plots which were also placed at a distance of 30-50 m from the nest plot. All characteristics were recorded in these plots as exercised in some earlier investigations (James & Shugart 1970;MacKenzie & Saely 1981;Clark et al. 1983;Sieg & Becker 1990;Liebezeit & George 2002).
Nest site and random site characteristics recorded during the study were tree number to be used subsequently for density calculations (trees/hectare), tree height (m), tree GBH (cm), basal area (m 2 ), the height of the first branch (m), distance from the nearest road (m), distance from nearest habitation (m), ground cover (%), shrub cover (%), canopy cover (%), canopy spread (m 3 ) and nest height (m). In addition, the species of nesting trees were identified and recorded. To ensure comparability and permit statistical analysis, the collected data were normalized beforehand. In the Qila (Aligarh Fort) area, the listed nest plots were labeled as NQi, while the random plots were labeled as RQi. On the other hand, in the University Campus area, the nest plots were labeled as NCi, and the random plots as RCi.

RESULTS
The Yellow-footed Green Pigeon's mating season begins in March and continues until July having renesting attempts towards the end of June and July. During this period, birds whose nests have been destroyed by predators seek to re-nest (Ayesha Mohammad Maslehuddin pers. obs. 31 May 2021). A total of thirty-one nests of Yellow-footed Green Pigeons The GBH of non-nest trees (0.46 ± 0.03) was slightly higher than that of the nest trees (0.42 ± 0.05) ( Figure  1), but there was no significant difference (t = -0.754, p >0.05) among them.
Tree species used for nesting by Yellow-footed Green Pigeons were Millingtonia hortensis, Prosopis juliflora, Azadirachta indica, Dalbergia sisso, Holoptelea integrifolia, Mangifera indica, Syzygium cumini, and Bombax ceiba. The number of nests on different tree species and the total number of individuals of each species, including those in the centre of random plots, are shown in Figure 3. The maximum number of nests were found on Millingtonia hortensis.

DISCUSSION AND CONCLUSION
The semi-natural plantations on the AMU Campus provide habitat to a wide variety of avifaunal species. The current study was one of the few attempts to acquire useful data regarding the ecology of species nesting.
Nest site characteristics show that Millingtonia

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hortensis, Azadirachta indica, and Dalbergia sissoo are essential nest tree species accounting for 69% of the total nest trees identified during the study period. These tree species ranged 11-25 m in height and were branched and bifurcated to provide a better place to hold the nest and a safe base for the pigeons to make their nests. Another reason was the abundance of these tree species at the study site.
The study revealed that the breeding season of Yellow-footed Green Pigeon is from late March to July in the study area. Nest building begins in early April, and they make open nests of mostly twigs (Image 3). Nests of Yellow-footed Green Pigeons are very simple in structure and made up of small twigs placed crisscrossed over one another. Both sexes were seen sharing nest building and duty of incubation, i.e., one of the breeding males or females continued to sit on the eggs while the other pair went foraging. As per observation, only one squab is hatched per nest. The duration from nest building until the fledgling left the nest was 39-44 days.
Nest building by Yellow-footed Green Pigeons was observed during the study period. Most of the nestbuilding activity occurred 0630-1000 h. Nest materials such as twigs were collected from dried branches of Holoptelea integrifolia, Azadirachta indica, Tectona grandis, Eucalyptus citriodora, Syzygium cumini, and Casuarina equisetifolia trees 15-30 m away from nest site by one of the mates. One of the breeding pair individuals broke suitable twigs from the branches and carried them toward the nest. The waiting individual on the tree gently arranged it into the nest securely. Also, it was observed that the individual carrying the twig never landed directly at the location where another mate was building the nest; instead, it would land on branches higher in the canopy and then move down towards the nest location cautiously. Apart from these, the frequency of nest-building trips was maximum during the 2 nd and 3 rd days of nesting, which gradually declined in the following days.
During the study, birds of prey such as Pariah Kites Milvus migrans and occasionally crows (Corvus splendens or C. macrorhynchos) were commonly seen preying on nests of Yellow-footed Green Pigeon. Some competitors like Common Mynas Acridotheres tristis, Eurasian Collared Dove Streptopelia decaocto, and Indian Palm Squirrel Funambulus palmarum mostly destroyed the nests; they forcefully entered the nest area of the pigeon, destroyed it and occupied the territory. Natural calamities like heavy rain and the storm destroyed most nests during the pre-hatching stage. Generally, the Yellow-footed Green Pigeons construct their nests on softwood trees, which are easily broken due to heavy rain and storm.
Association of yellow-footed Green Pigeons with the Black Drongo Dicrurus macrocercus during nesting season (Image 3) may be a great driver in predicting nests' success and subsequently emerging chicks. Around 40% of nests were successfully raised due to a Black Drongo nest in the vicinity of nests of Yellowfooted Green Pigeons. It has also been observed by Ali & Ripley (1987).
The success of nesting attempts by Yellow-footed Green Pigeons was determined based on the presence of hatched squabs in each nest. Of all the nests encountered, it was determined that only 35% achieved successful nesting, indicating the successful hatching of squabs. In contrast, the remaining 65% of nests were deemed unsuccessful due to their destruction by storms or abandonment caused by excessive disturbance, resulting in the absence of hatched squabs.
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