Seminar: Ferruginous Hawk (Buteo regalis) responses to human disturbance during the breeding season

Here is a young female Ferruginous Hawk sporting her new bands.On the left leg (her right leg) is the field-readable colour band and the silver band with serial number is on the right leg. Photo: Janet Ng.

Ferruginous Hawk on a nest, photo by Janet Ng

Today (14 December 2015) Cameron Nordell will give a public seminar as part of his MSc thesis defense. Come hear about his research at 1pm in the University of Alberta Biological Sciences Building, room CW 313.


Talk Summary:

The expansion of the human footprint across the world is increasing the number of interactions between humans and wildlife. Many studies have quantified wildlife behavioural responses to humans and this is an active area of research with practical implications for species conservation. However, changes to individual animals behaviour may be influenced by the properties of the disturbance stimulus itself, the effect of the environment in which the interaction occurs, and the individual’s past experience, but these potentially important effects have rarely been evaluated. Additionally it is unclear how individuals behave in the hours following the departure of human disturbance. In southern Alberta and Saskatchewan, I quantified the flight initiations from the nest by Ferruginous Hawks (Buteo regalis) in response to approaching investigators and used digital video systems to quantify their behaviour following investigator departure.

In Chapter 2 I studied the flight initiation distance from the nest (FID) by adult Ferruginous Hawks. FID was related to the actions of the investigator, the anthropogenic landscape around the nest and the number of previous visits to Ferruginous Hawk nests by investigators. Approaches by humans on foot illicit longer FIDs than those in a vehicle. Approaches driving on private access roads that were infrequently used by vehicles were related to increased FID. My data show that shorter FIDs are related greater number of vehicles that pass near a nest, demonstrating a relationship between human disturbances around the nest and FID. Finally, Ferruginous Hawk FIDs increased as the number of previous investigator approaches to that nest increased. Chapter 2 highlights the dynamic and complex nature of the decision to initiate flight from the nest and provides new insight as to why FID varies between and within species.

Having explored factors influencing the Ferruginous Hawk’s decision to change behaviour in response to human disturbance in Chapter 2, Chapter 3 focuses on the behavioural consequence through time when disturbed by humans. Here, I used digital video footage of Ferruginous Hawk nests to document nesting behaviour of adult males and females up to 12 hrs following an investigator disturbance, and test non-exclusive hypotheses that may explain differences in behaviour relative to undisturbed control periods. On average, across the 12 hr sample period, female Ferruginous Hawk spent significantly less time on the nest following investigator disturbance relative to controls, but individual variation was high. Delivery of prey items to the nest not significant different between disturbance and control sample periods. Disturbed female time on nest, initially lower than control periods, returned to normal over the course of our 12 hr sample period. The duration of reduced time on nest by the female varied with age and number of nestlings, such that female time on nest returned to normal sooner following a disturbance for young nestlings, and with larger broods. Thus, I found support for both the harm-to-offspring and parental investment hypotheses. This is among the first studies to identify that disturbed animals demonstrate behavioural differences from normal for up to 12 hrs following disturbance.

The ability to adapt flight initiation behaviour to human approaches and the consistent delivery of prey when disturbed suggests that, Ferruginous Hawks nesting in the highly anthropogenic regions of southern Alberta and Saskatchewan demonstrate the behavioural plasticity necessary to coexist with some human disturbance to the nest site. However, I also found instances of Ferruginous Hawk flight initiation at large distances, and that some individuals reduced nest attendance for lengthy durations following a human disturbance. Understanding how these extreme behaviours affect reproductive success of Ferruginous Hawks is likely essential to understanding human impacts on the Ferruginous Hawk population in Canada. My research was intended to contribute to the ongoing conservation effort for this species, and I discuss potential implications for management in Chapter 4. My research provides novel insight into disturbed behaviour and can inform management policies in the future as human development in the grasslands ecoregions expands and increases the number of interactions between humans and Ferruginous Hawks.