Introduction

The Common Black Hawk (Buteogallus anthracinus) is a bird of prey considered an opportunistic consumer (^{Schnell 1994}). The diet of the Common Black Hawk is highly variable depending on their distribution, prey availability, and season (^{Sherrod 1978}, ^{Hiraldo et al. 1991}). As resident top predators, hawks have an important role in controlling the populations of prey species (^{Ferguson-Lees and Christie 2010}). Main prey items include invertebrates (^{Stiles and Skutch 1989}, ^{Herrera and González 2017}), crustaceans and fish (^{Stiles and Skutch 1989}, ^{Hiraldo et al. 1991}, ^{Snyder and Snyder 2006}, ^{Barradas-García and Morales-Mávil 2007}, ^{Monge 2010}, ^{Escamilla-Cortés and García-Grajales 2024}), as well as reptiles, and some birds and mammals (^{Caldwell 1986}, ^{Wiley and Garrido 2005}, ^{Etzel et al. 2014}, ^{Shedd et al. 2021}).

Most of the records of mammal prey for Common Black Hawks are from the United States, with few records for the Neotropics. The occurrence of mammals in the diet of hawks is low, 3 - 6% (^{Sherrod 1978}) and mainly comprises rodents (^{Sherrod 1978}, ^{Wiley and Garrido 2005}, ^{Etzel et al. 2014}). There is only one record of bats of the genus Myotis in food remains reported in a raptor nest in Arizona (^{Etzel et al. 2014}). The present note documents a new record in the diet of the Common Black Hawk, and one of the few records from the Neotropics.

Methods

Observations were made in the El Cantil Blanco cave (19.39993, -96.55417; WGS 84) in Emiliano Zapata, Veracruz, Mexico (Fig. 1). The climate is warm sub-humid with an average annual humidity of 44%, a temperature range of 20-26°C, and total annual rainfall of 900-1300 mm (^{INEGI 2010}). The dry season occurs from October to May, and the rainy season from June to September (^{Gómez-Ortega 2018}). The vegetation comprises low deciduous forest, agricultural fields, and grassland (^{INEGI 2010}).

Figure 1 Location of the El Cantil Blanco cave in Emiliano Zapata, Veracruz, Mexico. 

The El Cantil Blanco cave is located 180 masl, about 10 m from the Paso de la Milpa River, a tributary of the Actopan River. This small cave extends to a depth of 12 m, starting from an entrance approximately 3 m high and 3 m wide, narrowing to 1 m high and 1.5 m wide at its most distal point. The cave is a refuge for bats, mainly Artibeus jamaicensis, Pteronotus personatus and Desmodus rotundus. Inside the cave, we found colonies of Artibeus jamaicensis and Pteronotus personatus roosting on the ceiling. Bat species were identified using field guides to the bats (^{Medellín et al 2008}) and mammals (^{Álvarez-Castañeda et al. 2015}) of Mexico.

We visited the cave every two weeks to make video recordings inside the cave to obtain data on the agonistic behaviour in a reproductive context of A. jamaicensis. During one of the visits to the cave, we recorded feeding behavior of a pair of Black Hawks at the entrance to El Cantil Blanco cave.

Results

On 18 December 2023, at 12:30 h, we observed a pair of Black Hawks manipulating a bat´s body. The hawks were identified as adult Common Black Hawks by their dark plumage and a white terminal band on the tail (^{Howell and Webb 1995}). The site at the entrance to the cave where we observed the hawks was a stone wall with a relatively flat surface, at a height of about 1 m from the ground. When the hawks perceived our presence, they flew away from the site.

One of the hawks dropped the bat's body, which was immediately collected and photographed. We identified the specimen as an adult male A. jamaicensis by the short interfemoral membrane, the absence of an external tail, and pointed ears (Fig. 2). The specimen had a body length of 78.5 mm and a forearm of 63.6 mm. The remains of the collected bat showed muscular rigidity, suggesting that the bat had died before we observed the hawks. There was also no odor of decomposition, therefore death was relatively recent. On inspection of the area at the base of the rock at the entrance to the cave, we found numerous bat remains along with bird pellets. Bat remains at the feeding roost were mainly wings and jaws. We counted parts of five jaws (Fig. 3a), all from A. jamaicensis, and 13 wing remains (Fig. 3b). The remains were not collected, but they were photographed and left in situ.

Figure 2 Bat Artibeus jamaicensis specimen dropped by a Common Black Hawk (Buteogallus anthracinus). Note the short interfemoral membrane, the absence of an external tail and the pointed ears. 

Figure 3 Bat remains found on a rock used as a feeding site by a pair of Common Black Hawk (Buteogallus anthracinus) at the entrance to a bat roosting cave in Veracruz, Mexico: a) jaw remains of Artibeus jamaicensis bats, b) remains of bat wings and bones. 

Consultation of previous studies found that reports of mammal prey in the diet of the Common Black Hawk mainly comprised rodents, with only two records of bats: Myotis sp (^{Etzel et al. 2014}); and an unidentified bat (^{Sherrod 1978}) both from Arizona, USA (Table 1).

Discussion

We provide the first direct observation of consumption of bat prey by the Common Black Hawk, and the first record for the Neotropics. Furthermore, our observation of the consumption of A. jamaicensis prey is the first species-specific record for the order Chiroptera (^{Sherrod 1978}, ^{Wiley and Garrido 2005}, ^{Etzel et al. 2014}). This result shows that bats are part of the diet of these raptors in our study area. We did not actually observe how the raptors capture the bats, however, this could be by active hunting. We propose that this is an opportunistic feeding behavior for Black Hawks in this coastal area of Veracruz, Mexico. This highlights not only the dietary flexibility of Black Hawks, but also their opportunistic feeding practices and exploitation of foraging sites.

Although Black Hawks feed on invertebrates (mainly crabs), fish, amphibians, reptiles, birds and mammals (^{Schnell 1994}, ^{Shedd et al. 2021}, ^{Escamilla-Cortés and García-Grajales 2024}), the occurrence of mammals in the diet of hawks is low compared to other food items (^{Sherrod 1978}). Reported mammalian prey mainly includes rodents, such as rats and mice, and a squirrel (Sherrod 1978, ^{Wiley and Garrido 2005}, ^{Etzel et al. 2014}), with few records of bats in the diet of the Common Black Hawk (^{Etzel et al. 2014}).

The muscular rigidity of the bat specimen dropped by one of the hawks suggests the specimen died some time before. The consumption of carrion by Common Black Hawks has been documented on only a few occasions (^{Carter and Wauer 1965}, ^{Brown and Amadon 1968}, ^{Abramson 1976}), although it is known to occur in Buteogallus sp. when food is scarce (Sánchez 2022). The context of our record, located in deciduous forest during the dry season, when there is reduced availability of food resources (^{Johnson and Schnell 2024}), could explain the greater dependence of Black Hawks on alternative food resources, such as bats. The low height, narrow width and shallow depth of the cave may provide a favorable environment for hawks to both capture live prey and access carrion, suggesting that birds strategically use this site for easy access to food.

The presence of two adults feeding at the same time suggests that this represents a breeding pair. Our observation in December coincides with the period of courtship, which occurs between December and January in the state of Veracruz, Mexico, with nesting between February and March (^{Barradas-García et al. 2004}, ^{Barradas-García and Morales-Mávil 2007}), similar to Trinidad and Panama (^{Mohan 2012}). The remains found near the cave entrance highlight the importance of future research to understand the Common Black Hawk’s foraging strategies and their ecological implications. This behavior adds to our understanding of the trophic ecology of Common Black Hawks. It highlights the importance of further research into the dynamics of predator-prey interactions to better understand the ecological role of these birds of prey within their ecosystems.