1. INTRODUCTION

House crow is a common bird of crow belonging to family Corvidae of order Passeriformes. House crow is omnivorous, scavenger bird. The food preference of house crow is highly opportunistic [1,2]. House crow also eat agricultural produce and stored food [3-8]. House crow is highly adaptive to the urban environment [9,10]. It is a strongly commensal, vocal, gregarious bird, generally unafraid of the public. Its abundance is closely associated with the human population up to the extent that non-dependent population may no longer exist [11]. Habitat abundance relationships suggest that house crows are highly dependent on anthropogenic food [1]. It is an invasive species, that is, negatively alters its new environment causing ecological, environmental, and economic damage [12-14]. Reports are available that mark house crow as the carrier of pathogens that cause diseases in human beings [13,15,16]. In India, the house crow is also associated with religious rituals. Feeding ecology of a bird is important aspect of the basic ecology of species concerned. Feeding behavior is the way, in which a bird exploits resources for feeding purpose. This explains how a bird species utilize their environment and help to identify the factors which are crucial for their survival and propagation [17]. The present study aims to describe some aspects of feeding ecology and behavior of house crow. Outcome definitely will help us to understand how population of this invasive bird species can be managed up to a sustainable level.

2. MATERIALS AND METHODS

The present investigation was carried out in certain parts of the city Prayagraj (Allahabad; 25°45’ N to 81° 85’ E) located in the southernmost part of the state Uttar Pradesh, India. Average elevation is over 90 m above sea level. Prayagraj has three seasons. Summer expand from March to June with temperature up to 48°C. Monsoon starts in June and lasts up to August and even up to mid-September having annual rainfall of 1027 mm. Winter runs from November to February, with average minimum temperature of about 9°C. Annual mean temperature is around 26°C. Recorded average relative humidity is about 53%. Prayagraj is the seventh most populous city of the state concerned and 36^th in country. Huge quantities of food scrap/human left over, animal remains, are produced in the city every day. City also covers considerable vegetation and river bank areas. Thus, studied city is right choice for the study of feeding ecology of house crow in an urban habitat.

Direct observations were made to record the food habits, feeding behavior, inter- and intraspecific struggles, and some other aspects of feeding ecology of the house crow. Focal animal sampling with 5 min interval was used to record individual feeding behavior. For group observation, all animal sampling together with ad-libitum were considered. All sampling methods were applied with procedure described by Altmann [18] and Lehner [19]. We observed group feeding up to the time participating species disintegrated or it was not possible to continue observation otherwise. Food stealing events were observed until house crow disappears or was beyond to tackle. We approximated food hoarding if captured/stolen food item was avoided to consume immediately and house crow flew away along with it up to the untraceable extent. Each study area has been visited 5 times in a month during period of April 2019 to April 2021. The observation started following sunrise and ended up to 09.00 AM and in evening 04.00 PM to 06.00 PM. Occasional visits were also made during day time whenever required. Identification of flora and fauna has been made using most preferred references. Bird’s counts were made at each study area using point count method [20]. Stopwatch and binocular (Olympus 10 × 50) have been used to observe feeding activity and bird’s counting whenever required with observation free of possible human interference. Photographs and videos were taken with the help of Cannon power shot digital camera with ×40 zoom (model no. SX430IS) with 20 mega pixel capacity. Suitable graphical presentation and statistical treatment have been made using Microsoft Excel 2007 version.

3. RESULTS AND DISCUSSION

Total 41 feeding grounds have been visited, of which only eight sites were located in neat clean places; rest resides in grubby/garbage collecting sites. House crow thus significantly feeds in unhygienic condition (calculated χ² value 9.01 > critical χ² value 3.84; P < 0.002). Feeding sites were almost full of human refuges, cooked left over, wastes from food stall, wastes recovered from vegetable/meat/fish market, animal remains, and other organic/inorganic constituents. It was perceived that roosting sites of house crow coincide with feeding sites. Principle diet consists of caterpillars, beetles, weevils, bugs, wasps, various other insects and small fishes, amphibians, reptiles, and fledglings. Kitchen leftover, human refuges, and various other edible organic/inorganic substances contribute a lot in its menu. Flowers and fruits of various plant species are also part of its diet. House crow frequently spotted to eat carrion and rotten meat [Table 1].

Table 1: List of food items observed to feed by house crow.

Food preference to above categorized items [Table 1] has been estimated by number of house crows spotted to feeding on it. House crows were found to significantly feed on human refuses and other miscellaneous food item (calculated χ² value 183.39 > critical χ² value 5.99; P < 0.0001) [Figure 1i]. Similar results were obtained when we consider feeding states (calculated χ² value 357.03 > critical χ² value 5.99; P < 0.0001) clearly indicating that house crow very unlike to feed on plant products [Figure 1ii]. In the early morning, house crows significantly feed on plant and animal source (calculated χ² value 4.79 > critical χ² value 3.84; P = 0.028) [Figure 1iii]. Rest of the day they mostly relayed on miscellaneous food items (calculated χ² value 49.14 > critical χ² value 3.84; P = 0.001) [Figure 1iv]. In addition to this, house crow significantly like to feed in the morning (calculated χ² value 37.33 > critical χ² value 3.84; P < 0.0001) [Figure 1v].

Figure 1: Pie chart showing various feeding aspects of Corvus splendens. (i) Number and percentage feeding on different food sources; (ii) number of feeding states under different feeding sources; (iii) number of feeding states at different feeding sources in the morning; (iv) number of feeding states during rest of the day at different feeding sources; (v) number of feeding states during morning and rest of the day; (vi) number of house crows feeding on major and minor plant feeder; (vii) number of feeding states at major and minor plant feeder; (viii) number of feeding states under different feeding patterns; (ix) number and percentage of inter and intraspecific competitive events; and (x) number and percentage of different feeding methods utilized. [Click here to view]

Koul and Sahi [17] in their study on feeding ecology of house crow in open agricultural fields listed the food items under three categories, namely, plant, animal, and other food items. House crow spends much time in searching for food on the ground and occasionally feeds on trees. The food preference of house crow is very broad and highly opportunistic; it includes seeds, fruit, grain, nectar, berries, bird’s eggs, nestlings, fledglings, reptiles, amphibians, fish, insects, carrion, and food scraps [1,2]. Alam and Nooralam [21] studied the feeding habit in urban habitat of Kolkata and reported that maximum count of house crow was made in residential area followed by commercial and public parks. They suggested that house crow prefers to feed significantly on residential wastes followed by food available at commercial places. Anjum et al. [22] reported feeding of house crow at a dumping site full of organic (fruit residues, vegetables remains, meat/chicken pieces, corn, and eggs) and inorganic (bulbs, plastic spoons, different packaging materials, cloths, pampers, animal dung, etc.) substances. Khan et al. [23] recorded foraging rhythms of house crow on some crops and found enhanced foraging activity in the early morning and late afternoon. Similarly, maximum feeding activity was observed in the early morning and in evening [14,22]. Minimum feeding activity was observed in the evening and middle of the day [14]. In the present study, we observed similar feeding characteristics.

Irrespective of the abundance of the various plant species, house crow significantly feed on five species, namely, Ficus religiosa, Azadirachta indica, Ficus racemosa, Ziziphus, Ficus indica, and Artocarpus lacucha (calculated χ² value 44.07 > critical χ² value 3.84; P < 0.0001) [Figure 1vi]. Plant species whose products were observed to frequently use as food source have been recognized as major plant feeder. Minor plant feeders were those occasionally visited by house crow for feeding purpose. Similar plant species preference has been calculated by considering occurrences of feeding states. About 72% of the total 432 feeding states were found to be associated with major plant feeder, that is, significantly more than 28% occurred on minor plant feeder species (calculated χ² value 35.65 > critical χ² value 3.84; P < 0.0001) [Figure 1vii]. Plantations such as citrus, sunflower, guava, unripe zizyphus, and jaman were frequently visited for feeding purpose by house crow [23]. Behrouzi-Rad [24] observed that most preferred trees for roosting and nesting purpose by house crow were Ficus bengalensis, Eucalyptus, and Ziziphus aucheri. Kaur and Sahi [25], during their study on community ecology of cattle erget, found vegetation consists of Acacia nilotica (babul), Dalbergia sissoo (sheesham), Eucalyptus, Zizyphus mauritiana, F. bengalensis, F. religiosa, and other plant species. House crow was one of important bird species of this community. Kaur and Kumar [26] found that six trees, namely, banyan (F. bengalensis), Jamun (Syzygium cumini), Mulberry (Morus alba), Neem (A. indica), Peepal (F. religiosa), and Sheesham (D. sissoo) harbor most of the bird diversity including house crow. We found similar pattern of vegetation with regional variation used by house crow for feeding and roosting purpose [3]. House crow significantly prefers to feed in congregation (calculated χ² value 96.31 > critical χ² value 3.84; P < 0.0001) [Figure 1viii]. Feeding observed to occur in group of 3/4 to more than 30 individuals [Figure 2a]. However, feeding solitary is not uncommon in house crow. It was observed that, in populated area they prefer to feed solitary, but in open field communal feeding is more common. House crow seen to utilize carcasses in congregation. Some individuals lie at the periphery of carcass waiting for their tern and rest feed untroubled. It seemed that waiting ones were probably act as sentries. It was important to note that when carcasses were intact they feed mutually along with feral dogs [2] possibly due to dependency to crack open the carcasses by them. Feral dogs rags the dead body that was subsequently utilized by the house crow. House crow was unafraid of any harm to be made by feral dogs [Figure 2b]. However, in case of cut open carcasses, house crow observed to have independent assess and showed aggression toward Sus scrofa that were feeding along [Figure 2c]. It was also seen that house crow feeds on ticks present on the body surface of S. scrofa and domestic buffalo (Bubalus sp). Whether the association of ticks to their host was beneficial/harmful, carriers never found tried to get rid of house crow. Probably tick’s feeding by house crow was a pleasant act. House crow seen to steal fish and rotten meat without any hesitation in places even with human interference. The instances of intraspecific competition were seen in feeding of carcasses and specific food offered to them. We have taken clawing, pecking, flapping of wings, and chasing as part of aggressive behavior. Interspecific competition was quite common. Acridothere tristis, Acridotheres ginginnianus, Gracupica contra, Passer domesticus, Bubulcus ibis, Egretta garzetta, Columbia livia, and Milvus migrans were bird species, house crow showed aggressive behavior. Interspecific competitive events were significantly more common in comparison to intraspecific competitive events (calculated χ² value 72.26 > critical χ² value 3.84; P < 0.0001) [Figure 1ix]. Interspecific competition of house crow has been observed with other birds and mammals [Table 2]. Competition with M. migrans was quite interesting. It was seen that out number of house crows and their unique strategy to occupy food item made them to surpass M. migrans. Food item was stolen by few individuals of a flock, while others involved in entangling the other party. In the meantime stealer hoarded the item at the nearby hoarding site. The incidences of food hoardings were also noticed to be associated with other feeding methods. Besides, house crow showed both aggressive and appeasement towards Macaca sp. and feral dogs [Figure 2d].

Figure 2: Photographs showing intra- and interspecific interactions. (a) Intraspecific interaction, (b-d) interspecific interaction with different animal species. [Click here to view]

Table 2: Some important animal species observed to share same feeding sites with house crow.

Feeding separately and becoming content with what got to eat were recognized as appeasement policy. In a 5 min of observation, significantly more time was spend in searching of food items and other unrecognized activities to actual feeding event (Calculated t-value 5.66 > critical t-value 2.04; P < 0.0001) [Figure 3]. House crow spends much time in searching for food [15]. Communal feeding is common in case of house crow. Communal feeding of house crow is well documented in case of valuable agricultural crops such as Wheat, Maize, Jowar, Groundnut, ripe fruits of fig, Mulberry, Chili, sunflower, and Grape which are some of the important crops on which losses caused by house crow depredation [3-8,23] as well as in case of carcasses [13]. Gobi et al. [27] observed that two house crows on either side of the food item were acting as sentries to alert the conspecifics while feeding. Sign of individual feeding can be traced in reports of stealing and food caching [28-30]. House crow dives into the water to catch stranded fish and forage on insects on the surface [31]. Interspecific competition has been noted in case of jungle crow (Corvus macrorhynchos culminatus) with aggressiveness toward house crow during food scarcity [32,33]. Kaur and Sahi [25], in their study on community ecology of cattle erget, listed the name of birds those share same feeding locality. Phalacrocorax niger, Ardeola grayii, Egretta garzetta, Vanellus indicus, Porphyrio porphyrio, A. tristis, Acridotheres ginginianus, C. splendens, and Dicrurus adsimilis are such bird species. Similar observation has been made by Kaul and Sahi [14]. Gobi et al. [27] found that Corvus splendens, Corvus culminatus, A. tristis [34], Turdoides caudatus, Funambulus palmarum, and Herpestes javanicus feed communally. Mishra et al. [35] found that four of the most common commensally and socially feeding species with Egyptian vulture are Milvus migrans, C. splendens, Bubulcus ibis, and Canis sp. They also observed that population of Egyptian vulture was positively correlated with those of house crow and feral dogs. We found similar communal structure at feeding sites in the present study.

Figure 3: Bar graph showing time spent by house crow in different activities in 5 min interval. [Click here to view]

Four types of feeding methods could be recognized, namely, searching, stealing, specific food offering, and food retrieved from cached sites. It was assumed that what house crow cached, retrieved completely later on. Searching was significantly most preferred feeding method followed by stealing. Specific food offering by men was also common, while food retrieval from cached side was little scare (calculated χ² value 277.33 > critical χ² value 7.81; P < 0.0001) [Figure 1x]. Stealing of food items is a common observation that we found to see or read in newspapers [13]. Food storing in corvids is well documented from centuries. Neuronal specialization of house crow with concern to food storing behavior has been studied in some detail by Srivastava et al. [30,36]. Specific food offerings to house crow has been reported by Saiyad et al. [37] and Kumar and Ojha [38]. The present finding is in agreement with these previous reports.

4. CONCLUSION

It is, therefore, concluded that house crow is omnivorous, highly opportunistic, and scavenger bird utilize urban resources to its best. It is possible due to its various ecological and behavioral adaptations in relation to act of feeding. It prefers to eat such items that are almost discarded by the others. It forages mostly in unhygienic places and thus trying to avoid unnecessary conflict. Furthermore, house crow roost communally close to the feeding source. So for behavior is concern, it is highly dramatic and plastic. Various feeding habits and strategies applied during community interactions specifically at the time of feeding make this bird far beyond others. Present work put forward some details to these things. It will be helpful to manage and utilize this amazing creature for human’s ecological and economic perspective.