Raptor Research

Raptors are fascinating and I have spent more than half my life watching and studying these wonderful animals. I have recently started to study these amazing animals for research. I have focused my research on Red tailed Hawks and Goshawks.

The northern goshawk (Accipiter gentilis) is the largest member of the accipiter genus in North America and the largest forest raptor.  Found throughout the Holarctic, northern goshawks are characterized by short, broad wings and a long tail, which is rounded on the end.  These features allow for rapid acceleration and agile maneuverability through dense forest trees.  They are powerful and aggressive hunters, living on a variety of prey including tree squirrels, hares, grouse, corvids, woodpeckers, and large passerines (Squires & Reynolds, 1997).  The species exhibits sexual dimorphism with larger females that have a slight difference in coloring pattern than males (Cooper, 1999).

Red Tailed Hawks are a highly adaptable raptor species that can be found throughout North America (Fitch et al. 1946). They are a valuable indicator species, as they are long-lived and an apex predator (Hogg and Nilon 2014; Denes et al. 2017). Specifically, RTHA employ a generalist diet, preying on various species of small mammals, birds, and reptiles (Fitch et al. 1946; Preston 1990; Morrison et al. 2016). Given their ability to prey on a large diversity of species, RTHA can be found inhabiting a variety of habitats, including rural, suburban, or urban (Minor et al. 1993; Bosakowski et al. 1996; Morrison et al. 2016). However, increased levels of urbanization also increases rates of car collisions, electrocutions, and consumption of rat poison (Richardson and Miller 1997; Hager 2009; Dwyer et al 2014; Morrison et al. 2016). Additionally, feral cats deplete rodent prey sources available for raptor species (George 1974).

As perch hunters, they search for prey while sitting on tall perches that give them a clear view of the landscape below (Janes 1984; Leyhe and Ritchison 2004). A suitable hunting perch is at least 2m high and stable enough to support the RTHA’s weight (Janes 1984). They are known to utilize both natural and artificial perches: natural being tall, open trees, and artificial typically being utility poles (Leyhe and Ritchison 2004). Large, perch hunters, such as RTHA, have shown preference for artificial perches as they are typically sturdier and contain less coverage that might obstruct their view (Malan and Crowe 1997). Regardless of perch type, the higher the perch, the larger their hunting radius becomes (Malan and Crowe 1997), which is valuable as their excellent eyesight allows them to spot movement within a 100-yard radius (Leyhe and Ritchison 2004.). Upon spotting a prey item, they will wait until it is in an ideal position that will allow them to efficiently capture the animal and either consume it on the ground or lift back into flight. (Fitch et al. 1946; Preston 1990). Perches are therefore a key component in supporting a population of RTHA (Fitch et al. 1946; Janes 1984; Preston 1990).

My hawk research focusing on these factors

  • Where do hawks go during the nesting time (how big is the territory) and then after nesting (do they stay in home range or move out)?
  • What is the prey base in active nest sites vs. inactive nest sites (is prey base a factor in nest renewal)?
  • What is the vegetation type and density in the nest area and territory?
  • Is one nest area better than another (survivorship of passage hawks)?
  • How are related are the hawks?
  • Can managers with the knowledge from previous parts of the project create suitable nesting sites for hawks from unsuitable habitat?