HUMANE PIGEON POPULATION MANAGEMENT USING AVIAN
CONTRACEPTIVE OVOCONTROL® P AT TRANSLINK SKYTRAIN STATIONS IN
THE LOWER MAINLAND OF BRITISH COLUMBIA, CANADA
by
Nadia Xenakis
B.Sc. (Honors), The University of British Columbia, 2018
A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF
THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
in
THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES
(Applied Animal Biology)
THE UNIVERSITY OF BRITISH COLUMBIA
June 2021
© Nadia Xenakis, 2021
The following individuals certify that they have read, and recommend to the Faculty of Graduate and Postdoctoral Studies for acceptance, a thesis entitled:
Humane Pigeon Population Management Using Avian Contraceptive OvoControl® P at TransLink SkyTrain Stations in the Lower Mainland of British Columbia, Canada
submitted by Nadia Xenakis in partial fulfillment of the requirements for the degree of Master of Science in Applied Animal Biology
Examining Committee:
Dr. Ronaldo Cerri, Professor, Applied Animal Biology, UBC Supervisor
Dr. Sara Dubois, Adjunct Professor, Applied Animal Biology, UBC Supervisory Committee Member
Dr. Kristen Walker, Professor, Applied Animal Biology, UBC Supervisory Committee Member
Dr. Sabina Magliocco, Professor, Anthropology, UBC Additional Examiner
Additional Supervisory Committee Members:
Dr. Alexandra Protopopova, Assistant Professor, Applied Animal Biology, UBC Supervisory Committee Member
ii
Abstract
Pigeon abundance in urban environments can result in human-wildlife conflicts in the form of excrement, disease, and nuisance behaviour. Managing human-wildlife conflicts using humane, sustainable and safe methods can help mitigate conflicts and ethically address the humane treatment of animals and the environment. Traditional methods of pigeon control include netting open areas, applying spikes to prevent perching, delivering low electric shock to birds on resting surfaces, lethal control through capture and culling, and flying raptors at chosen sites. These methods rely on principles of exclusion and removal which are not effective long-term, as pigeons typically find alternative spaces to evade exclusion attempts and populations slowly increase to pre-treatment size when culled. A relatively new method of management,
OvoControl® P is an avian contraceptive developed by Innolytics and is patented for pigeon control in Canada. The active compound in OvoControl® P is nicarbazin 0.5%, which disrupts the egg laying mechanisms in avian species, preventing the formation of a viable embryo. To test its efficacy as a pigeon management method for a major public transit network, eight TransLink
SkyTrain stations in the Lower Mainland region of British Columbia, Canada were chosen as study sites between March 2020 and March 2021. Four control site stations dispensed cracked corn and four experimental site stations dispensed OvoControl® P. Trail cameras actively recorded video clips at each station to provide population estimates and confirm pigeons were ingesting OvoControl® P. Measures of success monitored were daily population estimates and track alarm trigger data. Results found that stations dispensing cracked corn increased pigeon populations before and after treatment, while pigeon populations at stations dispensing
iii
OvoControl® P did not change before and after treatment. Further, an unexpected result was that higher numbers of pigeons inversely correlated to track alarm triggers, perhaps due to nesting behaviour. The use of OvoControl® P within a public transportation network has shown that it can be scaled and used as a long-term, humane management approach to deal with pigeon control and testing OvoControl® P over longer time periods is recommended to see if subsequent population declines can be observed.
iv
Lay Summary
Human-wildlife conflicts may arise with pigeons in urban environments, particularly where food and shelter resources are abundant. Public transit is a prime example, and this research was conducted at TransLink SkyTrain stations in British Columbia, Canada. Concerns involving pigeons include triggering track alarms and excrement that leads to an unfavorable environment for customers. This study measured the efficacy of using avian contraceptive OvoControl® P over one-year to manage pigeons at SkyTrain stations. Traditional pest control that was perceived to be a ‘quick-fix’ including the removal of pigeons, was previously employed as the main strategy although ineffective long-term. Results showed an increase in pigeons at stations dispensing cracked corn, while populations of pigeons at stations dispensing OvoControl® P did not change. It is recommended that TransLink continue treatment to assess if subsequent population declines are observed to assess if OvoControl® P could be effective long-term management for a significant human-wildlife conflict.
v
Preface
Chapter 3 and Chapter 4 are based on work conducted at TransLink SkyTrain stations across the
Lower Mainland of British Columbia, Canada by Nadia Xenakis under the supervision of Dr.
Ronaldo Cerri. Dr. Ronaldo Cerri, Dr. Sara Dubois and Nadia Xenakis were responsible for the design of the research project. Nadia Xenakis was responsible for collecting and compiling data and communicating with stakeholders. José Denis-Robichaud conducted statistical analysis of results. Dr. Ronaldo Cerri and Dr. Sara Dubois supervised the progress of the research project.
Ethics approval (A19-0001) was provided from the Animal Care Committee at The University of
British Columbia.
vi
Table of Contents
Abstract ...... iii
Lay Summary ...... v
Preface ...... vi
Table of Contents ...... vii
List of Tables ...... xi
List of Figures ...... xii
List of Symbols ...... xv
List of Abbreviations ...... xvi
Acknowledgements ...... xvii
Dedication ...... xix
Chapter 1: Introduction ...... 1
1.1 Thesis Aims ...... 1
1.2 Pigeons in a Cultural Context ...... 2
1.3 Pigeons and Urbanization ...... 4
1.4 Pigeons and Human-Wildlife Conflict ...... 5
1.5 Pigeons as Pests ...... 7
1.6 The Legal Status of Pigeons in North America ...... 9
1.7 Considerations for Human-Wildlife Conflict Management ...... 11
Chapter 2: Methods to Control Pigeon Populations ...... 13
2.1 Open Population Systems and Pigeon Dispersal ...... 13
vii
2.2 Exclusion and Deterrent Methods ...... 14
2.2.1 Spiking ...... 15
2.2.2 Netting ...... 16
2.2.3 Audio Deterrents and Visual Deterrents ...... 17
2.2.4 Raptor Presence ...... 18
2.3 Lethal Methods ...... 18
2.3.1 Avitrol® ...... 19
2.3.2 Culling ...... 20
2.4 Reproductive Control ...... 21
2.4.1 Pigeon Reproductive Biology ...... 21
2.4.2 Egg Removal ...... 22
2.4.3 OvoControl® P ...... 23
2.5 OvoControl® G ...... 25
2.6 Reproductive Control in Other Species ...... 26
2.6.1 Introduction ...... 26
2.6.2 Reproductive Control in Urban Wildlife ...... 26
2.6.3 Free-Ranging Wildlife ...... 28
2.6.4 Conclusions ...... 29
2.7 Summary ...... 30
viii
Chapter 3: Humane Population Management of Rock Pigeons (Columba livia) using avian contraceptive OvoControl® P at various TransLink SkyTrain stations across the Lower
Mainland of BC, Canada...... 32
3.1 Introduction ...... 32
3.1.1 Pigeon Abundance at TransLink SkyTrain Stations ...... 35
3.2 Results of OvoControl® P Use in Other Studies ...... 37
3.2.1 Study Predictions ...... 40
3.3 Goals of Research Project ...... 41
3.4 Methods...... 41
3.4.1 Data Collection ...... 44
3.4.2 Pigeon Population Video Monitoring ...... 46
3.4.3 Track Alarm Triggers ...... 50
3.4.4 Analysis...... 51
Chapter 4: Results ...... 53
4.1 Results ...... 53
4.1.1 Treatment and Total Number of Pigeons ...... 55
4.1.2 Treatment and Maximum Number of Pigeons ...... 57
4.1.3 Track Alarm Trigger Results ...... 59
4.2 Discussion ...... 63
4.3 Limitations ...... 64
4.4 Recommendations and Application of Findings ...... 67
ix
4.5 Future Research ...... 70
4.6 Conclusion ...... 71
References ...... 72
x
List of Tables
Table 1 Information on Eight Enrolled SkyTrain Stations ...... 43
xi
List of Figures
Figure 1. TransLink SkyTrain station and service map ...... 33
Figure 2. Train entering 22nd Street SkyTrain station ...... 34
Figure 3. Visual sample of OvoControl® P ...... 44
Figure 4. Sample experimental set up of camera and feeder ...... 46
Figure 5. Sample still frame from video footage ...... 47
Figure 6. Sample video monitoring sheet ...... 48
Figure 7. Sample data sheet for Surrey Central station ...... 49
Figure 8. Sample track alarm trigger data for December 2019 ...... 50
Figure 9. Maximum number of pigeons seen at one time in a day (light-color line) and total number of pigeons seen in a day (dark-color line) in eight SkyTrain stations in Vancouver
(Canada). Four stations (Renfrew, Stadium-Chinatown, VCC-Clark, and Metrotown) were experimental sites dispensing OvoControl® P, and four others (22nd Street, Surrey Central,
Lafarge Lake, and Joyce Collingwood) were control sites dispensing cracked corn...... 54
Figure 10. Predicted total number of pigeons observed in a day (± 95% confidence intervals) in seven SkyTrain stations in Vancouver (Canada), before and after the addition of treatment. Four stations (Renfrew, Stadium-Chinatown, VCC-Clark, and Metrotown) were experimental sites dispensing OvoControl® P, and three others (22nd Street, Surrey Central, and Joyce
Collingwood) were control sites dispensing cracked corn. Predicted values were obtained from a zero-inflated mixed effect model including the interaction between treatment and time-period
(before or after treatment), and the station and date as random effects (nobservations = 2,784 from
483 days and 7 stations). xii
...... 55
Figure 11. Total number of pigeons observed daily before and after the addition of treatment
(April 2020) in eight SkyTrain stations in Vancouver (Canada). In four stations (VCC-Clark,
Renfrew, Stadium-Chinatown, and Metrotown) OvoControl® P was dispensed and in the four others (Surrey Central, Lafarge Lake, Joyce-Collingwood, and 22nd Street) cracked corn was dispensed (nobservations = 3,007 from 458 days and 8 stations)...... 56
Figure 12. Predicted maximum number of pigeons observed in a day (± 95% confidence intervals) in seven SkyTrain stations in Vancouver (Canada), before and after the addition of treatment. Four stations (Renfrew, Stadium-Chinatown, VCC-Clark, and Metrotown) were experimental sites dispensing OvoControl® P, and three others (22nd Street, Surrey Central, and
Joyce Collingwood) were control sites dispensing cracked corn. Predicted values were obtained from a zero-inflated mixed effect model including the interaction between treatment and time- period (before or after treatment), and the station and date as random effects (nobservations = 2,784 from 483 days and 7 stations).
...... 57
Figure 13. Maximum number of pigeons observed daily before and after the addition of treatment (April 2020) in eight SkyTrain stations in Vancouver (Canada). In four stations (VCC-
Clark, Renfrew, Stadium-Chinatown, and Metrotown) OvoControl® P was dispensed and in the four others (Surrey Central, Lafarge Lake, Joyce Collingwood, and 22nd Street) cracked corn was dispensed (nobservations = 3,007 from 458 days)...... 59
Figure 14. Predicted change in the number of daily alarms according to the maximum number of pigeons observed at one time in a station (regression line ±95% confidence intervals), superposed to the observed data (points) in eight SkyTrain stations in Vancouver (Canada) from xiii
November 15, 2019 until February 28, 2021. The association was obtained from a zero-inflated mixed effect model including station and date as random effects (nobservations = 3,099 from 472 days).
...... 60
Figure 15. Maximum number of pigeons seen at one time in a day (light-color line) and number of alarms in a day (points) in eight SkyTrain Stations in Vancouver (Canada). Four stations
(Renfrew, Stadium-Chinatown, VCC-Clark, and Metrotown) were experimental sites dispensing
OvoControl® P. Four stations (22nd Street, Surrey Central, Lafarge Lake, and Joyce-
Collingwood) were control sites dispensing cracked corn.
...... 61
Figure 16. Predicted number of daily alarms (±95% confidence intervals) in eight SkyTrain stations in Vancouver (Canada), before and after the addition of treatment (April 2020). In four stations (VCC-Clark, Renfrew, Stadium-Chinatown, and Metrotown) OvoControl® P was dispensed and in the four others (Surrey Central, Lafarge Lake, Joyce-Collingwood, and 22nd
Street) cracked corn was dispensed. Predicted values were obtained from a zero-inflated mixed effect model including the interaction between treatment and time-period (before or after treatment), and the station and date as random effects (nobservation = 2,888 from 441 days and 8 stations).
...... 62
xiv
List of Symbols
® Registered Trademark
$ Dollar Sign
% Percent Symbol
€ Euro Sign
xv
List of Abbreviations
BC British Columbia
BCRTC British Columbia Rapid Transit Company Ltd.
BC SPCA British Columbia Society for the Prevention of Cruelty to Animals
CAD Canadian Dollar
DNC 4,4'-dinitrocarbanilide
GnRH Gonadotropin-Releasing Hormone
HDP 4,6-dimethyl-2-pyrimidinol km Kilometre lb Pound mm Millimetre
PZP Porcine Zona Pellucida
SGARs Second Generation Anticoagulant Rodenticides
US United States
USD United States Dollar
xvi
Acknowledgements
I would like to first acknowledge the privilege I have to conduct my work on The University of
British Columbia campus that sits on the ancestral and unceded lands of the Musqueam People. I would like to extend my deep gratitude and appreciation to Dr. Sara Dubois for her mentorship, patience, guidance, and willingness to help me carve a path for myself – none of this would have been possible without you. Thank you to Dr. Ronaldo Cerri for ensuring I had all possible resources available to me and providing an unwavering and abundant source of positivity and support. I would like to extend gratitude to my committee members, Dr. Kristen Walker and Dr.
Alexandra Protopopova, your input has been invaluable, it has been an absolute pleasure to work with both of you. To Dr. José Denis-Robichaud thank you for making sense of the data - you are incredibly brilliant, and I am so thankful. To the Animal Welfare Program, thank you for giving me a safe, constructive, positive, and supportive environment filled with compassionate and remarkable colleagues.
I would like to extend gratitude to TransLink for taking a risk and exploring novel and progressive pest management methods - your support, trust, and willingness to explore alternatives is inspiring. Research like this would not be possible without it. To Terminix, you have been incredibly accommodating, and it has been such a pleasure to work with all of your staff. Thank you to Mitacs for helping fund this research and for providing support and guidance throughout the research process.
To my friends and family - there aren’t words that I could hope to string together that would adequately express my love and gratitude for your support and presence. Chad, for your belief in me when I lacked it in myself; for reminding me to eat, breathe, and relax; and for encouraging xvii
my return to school, I am eternally grateful. To my non-human family, Hachi, Arty, and Kimmi, your company was the greatest gift through this journey.
xviii
Dedication
I dedicate this work to the pigeons for teaching me resiliency.
xix
Chapter 1: Introduction
Pigeons currently span every continent outside of Antarctica, having spread successfully from their native origins in Europe, North Africa and the Middle East, arriving in North America over
400 years ago (Shapiro & Domyan, 2013). As pigeons have thrived prolifically in urban environments across North America, the aim of Chapter 1 is to provide a background through their cultural context and explore related human-wildlife conflicts.
1.1 Thesis Aims
Animals considered pests in urban societies typically have their ecological and inherent value diminished by this label, making their removal or suppression in favor of human interests appear justified (Oogjies, 1997). Although it is not contested that management of nuisance animal populations can benefit conservation goals, human health, and general urban living (Lauber, et al., 2007), the aim of this thesis is to support a long-term management strategy for pigeons that promotes modified coexistence.
Chapter 1 aims to provide context and history for pigeons in culture by discussing their origins and important historical highlights; providing background on their success in urban environments and consequential human-wildlife conflicts; and discussing their role most commonly as pests. Understanding these aspects of pigeon populations when developing a tool for population control can provide context, understanding, and appreciation that is typically removed when pigeons are labelled ‘pests’ and hence, are more justifiable to kill under this label.
Topics discussed in Chapter 2 aim to provide an understanding of previous and existing methods and technology used to control or remove pigeon populations. These existing methods broadly fall under two categories: removal or exclusion. Considerations for developing a 1
management solution to pest populations will be discussed, followed by an assessment of different techniques commonly used by pest control professionals and their efficacy.
Reproductive control will be introduced in this chapter as it is the focus for experimental research in Chapter 3, including development and current use.
The experimental research of this thesis will be presented in Chapter 3 and will detail the human-wildlife conflicts currently occurring at TransLink SkyTrain stations and the methodology used to assess reproductive control of pigeons and its general success. Chapter 4 will discuss results and how they relate to broader applications, wildlife management in general, and long-term applicability of this methodology in terms of cost, feasibility and projected results.
1.2 Pigeons in a Cultural Context
In an attempt to find the origin of pigeons and their relation to humankind, Blasco and colleagues (2014) found evidence that Neanderthals consumed Rock Doves regularly and were able to show a clear connection linking Rock Doves to Gorham’s Cave (Gibraltar), which predates modern humans and transcends human lineage. The term ‘Rock Dove’ refers to domestic and feral pigeons which are breeds of Columba livia, although there are approximately
300 species of pigeons and doves belonging to family Columbidae (Shapiro & Domyan, 2013).
Culturally, pigeons have held significance to humans. It is believed that pigeons originally had an important ceremonial presence, as well as providing a source of food, for Egyptians at least 4,000 years ago (Shapiro & Domyan, 2013). Charles Darwin used the vast diversity in pigeons in The Origin of Species to demonstrate the similarities between natural and artificial selection, and often referred to domestic pigeons when conveying his thoughts on natural selection (Darwin & Kebler, 1859). As stated by Andrew Blechman in the book Pigeons, 2
“[Pigeons] have been worshipped as fertility goddesses, representations of the Christian Holy
Ghost and symbols of peace. They’ve been domesticated since the dawn of man and utilized by every major historical superpower from ancient Egypt to the United States of America. Nearly a million pigeons served in both World Wars and are credited with saving thousands of soldiers’ lives” (Blechman, 2006 pg. 4). Pigeons played a role in the United States Army as couriers until the program ended in 1957 (Blechman, 2006 pg. 38), and were used to demonstrate principles of operant conditioning in attempts to use pigeons to deliver guided missiles (Skinner, 1960).
Ecologically, pigeons play a major role in the formation of wildlife habitat as consumers of seeds and agents of seed dispersal (Butcher & Bocco, 2009). They are incredibly resilient to the ability of supporting substantial predation, serving as an important food source for many birds of prey (Cappocia et al., 2018). Furthermore, pigeons are studied in growing research fields which observe factors shaping diversity in urban habitats, such as human activity, landscape cover type and noise (Luniak, 2004; Beausoleil et al., 2016; Aronson et al., 2017).
Recreationally, pigeon racing and pigeon shooting are activities that are still practiced today, with historical events such as pigeon shooting being a part of the 1900 Olympic Games in Paris
(Mallon, 1998). Although controversial, an annual pigeon shoot was held in Hegins,
Pennsylvania from 1934 to 1998. It garnered enough opposition from animal rights activists that involvement from the Pennsylvania Supreme Court ended the tradition in 1999 (Bronner, 2008).
Pigeon racing is a hobby that some dedicate their lives and resources to, with the most expensive and recent sale of a pigeon named New Kim being USD$1,890,000 (Rossignol & Biesemans,
2020).
3
Whether appreciated or reviled, pigeons have a long and important history with humans and permeate through different aspects of life and culture. Currently, it is estimated that there are approximately 165-330 million individual feral pigeons globally (Farfan et al., 2019).
1.3 Pigeons and Urbanization
When compared to other species of wildlife in urban settings, pigeons have been exceptionally successful. The Rock Dove, the wild ancestor of the feral pigeon, had a preferred habitat of nesting on cliff edges, rocky habitats and the entrances of large caves (Blasco et al.,
2014); while the modern pigeon has made use of the abundance of building ledges, overhangs and bridge structures that simulate natural areas for nesting, roosting and perching (Spennemann
& Watson, 2017). Although studies are limited on the historical growth of pigeon populations in cities, some indicate that a significant increase in feral pigeon populations can be attributed to the last half of the 20th century in Europe and North America (Johnston & Janiga, 1995). Broadly, reasons for their success may include low levels of predation, flexible resource use for nesting material, as well as increased heat in urban environments due to human traffic, housing, and businesses, that reduce cold stress in the winter, in addition to breeding year-round in most temperate climates (Pellizzari, 2017).
Cappocia and colleagues (2018) observed the distribution of pigeons and concluded that there is a strong connection between pigeons and vacant buildings, essentially, areas that have moderate protection from the environment and a reliable food source. In fact, pigeons are particularly adept at learning to associate stimulus with the presence or absence of food and will remain in environments with food-signaling stimuli such as dumpsters or areas of high human traffic (Zentall et al., 1992). This contributes to the feral pigeon population of a community being 4
directly related to the amount of food available to the pigeons (Spennemann & Watson, 2017).
Aside from farmlands providing food to some urban pigeon populations when located nearby, there are food sources found in urban parks and private gardens, as well as ‘volunteer’ sources from humans intentionally feeding the populations and ‘waste’ feeding through spillage or garbage cans and dumpsters (Spenneman & Watson, 2017).
As animals with the ability to eat a wide variety of foods, pigeons do not need to hone complex foraging skills, but rather must typically forage for food extensively (Johnston &
Janiga, 1995). However, urban environments offer an abundance of forage availability allowing pigeons to expend minimal effort and rather redistribute this effort into reproduction (Richardson et al., 2016).
As pigeons seem to thrive in tandem with human existence, it is not unreasonable to consider human behaviour and urban living when approaching how to best manage pigeon populations.
For many people, pigeons may be seen as a connection to wildlife in urban environments where wild animals are scarce. Understanding that cities are their own unique ecosystems with particular enabling factors due to human influence, will aide in better understanding human- wildlife coexistence of urban wildlife. Humans and pigeons are interconnected and understanding this relationship can assist in managing pigeon populations in urban environments to minimize human-wildlife conflicts.
1.4 Pigeons and Human-Wildlife Conflict
Human-wildlife conflicts can broadly be defined as interactions or situations where actions performed by either humans or wildlife have an adverse effect on the other (Conover, 2002).
5
Human-wildlife conflicts involving pigeons in most environments can broadly be attributed to two main sources of concern: excrement and risk of disease. Concerns regarding excrement can involve being visually unappealing; slippage for those passing by; damage to infrastructure; and disease, as when pigeon excrement dries, the infection vector can present as dust which can be inhaled (Pellizzari, 2017).
Due to the wide variety of foods that pigeons are able to consume, urban-sourced diets tend to cause more acidic excreta when compared to natural diets consisting mainly of seeds (Rose et al.,
2006). Birds that perch and roost may defecate on buildings and infrastructure, which aside from being aesthetically unpleasing (Mansfield, 1990; Murton et al., 1972b; Howard et al., 1991), can cause chemical deterioration of architecture (Rose et al., 2006). Nearly 20 years ago, the economic consequences of this were substantial as seen in Munich, Germany where approximately €1 million was spent annually (Vater, 2002) to remove excrement; while Cologne,
Germany spent roughly €250,000 on only the maintenance of 38 rail underpasses (Berger, 2002).
In the United States, it is estimated that pigeons were responsible for roughly US$1 billion annually in damages (Pimentel et al., 2000) 20 years ago, with current estimations unknown.
Disease risk from pigeons has been well-studied and pigeons are a potential source of
Cryptococcus spp. and other pathogenic yeasts (Costa et al., 2010). An analysis of pigeon droppings identified species from the viral families Circoviridae, Parvoviridae, Picornaviridae,
Reoviridae, Adenovirus, Astroviridae and Caliciviridae, in addition to plant and insect viruses thought to originate from consumed food (Phan et al., 2013). Generally, the prevention of contact with pigeon excreta can be an effective precautionary measure for the general public however, immunocompromised humans may be at a greater risk for respiratory disease based on documented cases (Kuiken et al., 2018). Newcastle disease, caused by a Paramyxoviridae virus, 6
is associated with pigeons and is one of the most important viral diseases in poultry worldwide
(Alexander & Capua 2008). This is due to financial impacts and trading restrictions placed on countries where outbreaks have occurred, in addition to potential severe flock mortality where infection occurs (Alexander & Capua, 2008). However, it is important to note that despite concerns regarding pigeons and the potential of disease spread, it does not appear that pigeons have any more disease-spreading capacity than other urban birds (Angier, 1991; Helen, 2001;
Kelley, 2000).
A case study to illustrate human-wildlife conflicts involving pigeons presented in Butte,
Montana by Richardson and colleagues (2016) aimed to address concerns from local business owners over damage from the local pigeon population. When the business owners were surveyed, the vast majority had negative opinions about the pigeons, while only 12% had a positive outlook towards the animals (Richardson et al., 2016). Farfan and colleagues (2019) also conducted a survey on attitudes towards pigeons in residents of 24 buildings between Estepona and Malaga, Spain, and found that residents in all areas complained about excrement problems related to breeding and roosting pigeons.
As people continue to urbanize and pigeons continue to successfully thrive in urban environments, human-wildlife conflicts are bound to continue (Fagerstone et al., 2010; Massei &
Cowan, 2014). Finding effective ways to mitigate and address these conflicts regarding excrement and disease risk will likely become of increasing interest.
1.5 Pigeons as Pests
Increasing rates of human-wildlife conflicts, the ability to breed year-round in some climates, and generally perceived overabundance (Pelizzarri, 2017), can cause animals to be deemed pests. 7
This label is often assigned to animals viewed as scavengers, or animals that are thought to be useless through a human-centered lens (Herda-Rapp & Goedeke, 2005). Additionally, animals seen as pests are more likely to be thought of as being unattractive or not charismatic by the general public (Micheal, 2004), making lethal control or extermination of the animal appear more socially acceptable (Oogjies, 1997).
A comprehensive review by Jerolmack (2008) analyzing news article headlines in The New
York Times dating back to 1874, offers insight into the cultural shift in viewing pigeons as pests.
Early headlines from 1874-1909 express outrage over pigeon shootings, however in 1945, the first article appears that mentions a specific disease, ornithosis, associated with pigeons. This is followed soon after in 1963 by a New York health official relating two human deaths to
Cryptococcal meningitis, a disease carried by pigeons, and campaigning for the city to rid itself of 5,000,000 resident pigeons. In 1966, the term ‘rats with wings’ was coined and attributed to a quote of the parks commissioner which, as explained by Jerolmack (2008) states “in no certain terms, morally implicated pigeons as ‘vandals’, and slinging the term rats with wings at them is consistent with the tone of the piece in which derogatory language was used to indict homeless and homosexuals” (Jerolmack, 2008 pg. 81).
These comparisons are important to highlight as they suggest that there is a relation between how humans treat animals and how they treat each other (Arluke & Sanders, 1996; Irvine, 2004;
Philo, 1995). An equally egregious comparison was made in a 1977 article entitled “Going to
War with Pigeons – And Losing” which suggested that pigeons are not only undesirable, but also immoral and tied to undesirable human beings, referencing the homeless populations in urban centers (Brown, 1977). Recently in popular culture, in 1980 Woody Allen popularized the term
‘rats with wings’ in the movie Stardust Memories (Stardust Memories, 0:26:29). In 2005, a book 8
entitled “101 Tried and True Pigeon Killin’ Methods” (Jones, 2005) was published, reinforcing pigeons as pests in North American culture.
Understanding cultural ideologies surrounding animals is important. The wellbeing of animals labelled ‘pests’ can be influenced by whether there is public concern for their welfare, and the acceptance of certain population control methods can be heavily influenced by this label
(Oogjies, 1997). Public attitudes, particularly expressed through media and campaigns, can shift values from either supporting the complete eradication of a population through use of lethal control or adopting management with coexistence (van Eeden et al., 2020) as discussed in
Chapter 2.
1.6 The Legal Status of Pigeons in North America
The legal status of pigeons in North America is dependent on which country, province, city or state you reside in. Relevant to North America is the Migratory Birds Convention Act, however, as pigeons are not migratory birds and are not considered a native species by signatory countries, pigeons are not protected under this Act (Government of Canada, 1994).
In the United States, the Preventing Animal Cruelty and Torture Act makes animal cruelty a federal crime, specifically the action of crushing animals (Government of The United States of
America, 2019) However, there are numerous exemptions for general animal suffering for agricultural and veterinary practices. Similarly, the US Animal Welfare Act pertains mostly to animals bred for commercial sale, used in research, transported commercially or exhibited
(Government of The United States of America, 1966). This legislation intended to protect animals but does not extend to pigeons, leaving them legally vulnerable. Under the regulations of the US Fish & Wildlife Service, all wild birds are protected under federal and state laws except 9
pigeons, English sparrows, and starlings (Migratory Bird Program, 2018). Individual state laws and city bylaws can also determine whether it is legal to kill pigeons in specific locations. In most cities, it is illegal to discharge a firearm within city limits, so for this reason, it would be illegal to shoot a pigeon within the indicated jurisdiction. Aside from this restriction, hunting regulations also vary by state and it may be legal to hunt pigeons year-round or there may be restrictions tied to a specific hunting season.
In Canadian law, the federal Criminal Code of Canada (sections 444-447) addresses animal cruelty and states that every individual commits a crime who “willfully causes or, being the owner, willfully permits to be caused unnecessary pain, suffering or injury to an animal or bird”
(Section 445.1) (Government of Canada, 1985). Provincially, the rules regarding pigeon control may differ (whether permits required or not), but generally it is legal to kill pigeons. For example, under the BC Wildlife Act (Government of British Columbia, 1996), permits are required to kill any birds except for domestic pigeons, starlings, crows, magpies, English sparrows and brown-headed cowbirds. Similarly in BC, the Prevention of Cruelty to Animals Act
(Government of British Columbia, 1995) allows for standard industry practices when controlling pests, permitting the use of lethal methods. This is similar to requirements in Prince Edward
Island (Government of Prince Edward Island, 2020). Under Ontario’s Fish and Wildlife
Conservation Act (Government of Ontario, 1997), a small game license is easy to obtain and allows for the free hunting of pigeons in the province; similar legislation exists in Quebec under
An Act Respecting the Conservation and Development of Wildlife (Government of Quebec,
2012).
Relevant legislation may also exist at a municipal level with bylaws pertaining to shooting firearms in public. An interview with Constable Wendy Drummond of Toronto Police Services 10
highlights the use of firearms as being the most relevant factor in municipal bylaws for killing animals: “any discharge of a pellet gun with intent to kill would result in a weapons charge.
Snapping their little necks, quickly and humanely, would be tolerated, she said, "unless, you know, we find 100 dead pigeons" (Vanstone, 2007 para. 7). In BC for example, a person is not required to have a hunting license to kill pigeons as they are schedule “C” animals that “can be captured or killed anywhere and at any time in BC” (British Columbia Ministry of Environment,
2021). However, if wanting to use a gun in order to kill a pigeon in Vancouver, Bylaw 2280 states “any person firing or discharging, or permitting to be fired or discharged, any firearm within the City without first having secured such permit shall be deemed to be guilty of an infraction” (City of Vancouver, 1933).
Overall, pigeons are unprotected under federal, provincial, and municipal law which legally allows for their removal through lethal methods unless in violation of firearm restrictions.
1.7 Considerations for Human-Wildlife Conflict Management
Although many different approaches to human-wildlife conflicts involving pigeons have been used in North America, this thesis will evaluate various types of wildlife control techniques through the ethical framework provided by Dubois and colleagues (2017). This set of seven international consensus principles for addressing ethical wildlife control requires management actions to: modify human practices when possible; justify the need for control; have clear and achievable outcome-based objectives; cause the least harm to animals; consider community values and scientific information; include long-term systematic management; and to base control on specifics of the situation. This thesis will evaluate current practices for pigeon control
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including exclusion, lethal and reproductive methods using these considerations and ultimately scientifically evaluate the use of reproductive control in an urban environment.
Others have advocated that any method other than long-term management of human-wildlife conflicts through reproductive control or exclusion methods, will result in short-term successes through culling or removal being repeatedly used, without a sustainable solution ever being reached (Clayton & Cowan, 2010). The importance of evaluating community values is also key to assessing conflicts as the intolerance for lethal wildlife management continues to grow
(Fagerstone et al., 2010). Given that locations where pigeon control is desired each have their own unique enabling factors and niches that contribute to successful populations of pigeons
(Harris et al., 2017), this confirms that basing control on the specifics of the situation is necessary since one cannot use a broad guide to manage every individual situation and ecosystem of each environment.
By applying these principles to the control of pigeons, this thesis proposes to assess the efficacy of a non-lethal method of wildlife management as an alternative to traditional methods reviewed in Chapter 2. Early research has focused on understanding effects of reproductive control on individual animals (Ransom, 2014), but understanding the efficacy of fertility control as a way to manage populations remains largely unanswered in pigeons. This will be explored in
Chapter 3 following examples of fertility control demonstrated in other species in Chapter 2.
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Chapter 2: Methods to Control Pigeon Populations
This chapter reviews common pigeon population management methods currently available for use by both registered pest control applicators and non-certified applicators. Management methods discussed fall under three categories, the first being exclusion methods, including spiking, netting, audio and visual deterrents, and the use of raptor presence. The second category is the use of lethal methods, including culling and the chemical agents (i.e., Avitrol®).
Certification of using chemical substances for pest control is mandated nationally in Canada
(Government of Canada, 2009) and the United States (United States Environmental Protection
Agency, 2020). The third category includes reproductive methods of control such as the use of physical egg removal and avian contraceptive (i.e., OvoControl® P). The use of reproductive control in other species of free-ranging animals will also be discussed in this chapter.
2.1 Open Population Systems and Pigeon Dispersal
Controlling pigeon populations can involve manipulating one of two population dynamic factors: either increasing or decreasing mortality, or increasing or decreasing reproductive rates
(Macdonald, 2013). When examining populations and choosing a population management method it is important to consider whether a population is ‘open’ or ‘closed’. Open populations of animals are open to immigration and emigration, while closed populations are not, typically due to physical barriers such as bodies of water, habitat fragmentation or human-constructed infrastructure (Ransom et al., 2014). For the purpose of this thesis, all feral pigeons will be considered open populations of animals that are able to move freely and without obstruction.
Due to many wildlife species being free-ranging open populations, reproductive control has not been used or studied significantly as a method of population management due to the inability to 13
ensure animals remain in areas treated with reproductive control, and animals not treated with reproductive control, do not move into the area (Malcolm, 2008).
Information related to the dispersal and home range of pigeons is scarce with little data available about the rate of exchange between pigeons among cities (Giunichi et al., 2007).
However, one study suggests pigeons can cover short distances outside of city limits, less than
10 km (Rose et al., 2006) and another proposes that feral pigeons characteristically have short
(less than 0.1 km) natal dispersal distances (Johnston & Janiga, 1995). A further study by
Richardson and colleagues (2016) looked at dispersal to help address complaints about feral pigeon populations from local business owners, and found that there was minimal dispersal between colonies, the largest being 6.1 km, travelled by two individuals. Richardson and colleagues (2016) also found that none of the adult individuals were detected in another colony and only one juvenile bird was detected in a separate colony 0.11 km away from their original banding site. Overall, their findings are consistent with Murton and colleagues (1972a) who suggested pigeons are relatively sedentary as 85-87% of marked pigeons in their study moved less than 0.09 km away from the marking point. Although dispersal research is limited, it is important to understand pigeon population dynamics when determining appropriate population control methods.
2.2 Exclusion and Deterrent Methods
Exclusion methods are popular in use due to their perceived efficacy and non-lethal effects.
However, each treatment site is unique in structure and population, and broad claims of efficacy made by pest control applicators and companies rarely apply (Harris et al., 2017). Exclusion methods that modify an environment with physical barriers to prevent pigeons from entering or 14
perching are also widely used because they are highly acceptable for the general public (Giunchi et al., 2012). Exclusion methods discussed in this section will include spiking, netting, audio and visual deterrents as well as the use of raptor presence. Additional exclusion methods include bird jolts, adhesive gel bird repellent and fog aerosols that will not be discussed further in this chapter due to a lack of empirical evaluation of their efficacy.
2.2.1 Spiking
Spiking involves the use of anti-perching equipment including sprung wires (Hutton, 2005) and bird spikes (Seamans et al., 2007). There are a variety of brands and materials available that can be applied to surfaces that claim to prevent pigeons from roosting and perching. Harris and colleagues (2016) monitored the use of multiple pigeon management methods at University of
South Africa's Muckleneuk campus and found that bird spikes seemed the most effective of their chosen deterrents. In some areas they were able to decrease pigeon populations by 50%, however, it is important to note that bird spikes were used in tandem with visual and audio deterrents in the same time frame (Harris et al., 2016). These results support those of Seamans and colleagues (2007) who also found bird spikes to be effective in an airport setting. Harris and colleagues (2016) also noted that excrement and debris could get caught in the spikes making them ineffective as debris levels accumulate to the height of the spike, noting that ongoing maintenance and monitoring would be essential to maintain efficacy. The strategy of bird spike placement and building structure is an important consideration. If alternative perching sites are available in the immediate vicinity, such as open ceiling boards or overhangs, the efficacy of the bird spikes are diminished (Harris et al., 2017). Generally, bird spikes do not alter the actual population of pigeons at a given site (Krimowa, 2012) and are only capable of displacing animals 15
to nearby sites that do not have any population management treatments (Mooallem, 2006;
Giegenfeind, 2013).
2.2.2 Netting
Netting is a method that involves applying a screen or large net to cover open areas that pigeons can access, this may include a hole in a wall of a building, open ceiling or open-ended tunnels that pigeons can fly through (Hockenyos, 1962). Nets can be made with a tensioned wire framework with an approximate aperture size of 19-25 mm for pigeons to be completely excluded by size and must be anchored securely so that there are no gaps between the net and adhesion surface (Muxlox, 2019). Although no empirical evaluation has specifically looked at the efficacy of netting to exclude pigeons from a desired site, it is reasonable to assume that similar maintenance requirements and efficacy would occur to that from bird spiking as it excludes birds from a desired area and is dependent on the installation and structure of the building. It is important to note that the cost of netting compared to spiking can be prohibitively more expensive as it is labour intensive and requires maintenance. However, netting is considered the ‘gold standard’ for pest control companies if applied effectively to ensure there are no entrance locations for pigeons (Muxlox, 2019).
Netting is not without public criticism however, as a newspaper in the UK reported that pigeons had died at a local supermarket after being left trapped in netting intended for their exclusion for over a week (Sexton, 2020). Additionally, in Scotland disputes over netting applied to a bridge at a railway station that left some pigeons trapped and unable to escape, prompted complaints from people passing by (Shipley, 2020). Overall, netting is effective at deterring pigeons from entering buildings or urban environments when applied correctly and strategically, 16
but can be costly to implement, depreciate in effectiveness if not maintained (Hutton, 2005), and may result in criticism if not monitored for trapped birds.
2.2.3 Audio Deterrents and Visual Deterrents
Audio deterrents consist of modulated frequencies being released at desired sites to deter pigeons from areas due to their unpleasant frequency or mimicry of predators (Beason, 2014).
Modulation of audio deterrents can be random or constant but are typically ineffective as birds quickly habituate to signals (Beason, 2014). Studies on the reactions of starlings to audio deterrents have found starlings to react initially to noise but habituate within days (Thomson et al., 1979; Cole et al., 1983; Johnson et al., 1985). Although the efficacy of audio deterrents has not been studied specifically in pigeons, it is reasonable to assume the outcomes of audio deterrents would be relevant as pigeons have a similar frequency sensitivity as starlings (Beason,
2014).
Visual deterrents can include an array of products such as decoys (Harris & Davis, 1998), moving lights and objects (Blackwell et al., 2002), and threatening imagery or reflective items
(Harris et al., 2016), with the intent of impersonating danger or making sites less desirable for perching. Harris and colleagues’ (2016) University of South Africa's Muckleneuk campus study used visual deterrents to reduce pigeon populations and were successful by an average of 33% reduction. However, the visual deterrents were found to be generally ineffective due to habituation by the pigeons that occurred within two years, which is consistent with previous studies assessing the efficacy of visual deterrents (Hutton & Dobson, 1993; Godin, 1994; Harris
& Davies, 1998; Hutton, 2005; Fukuda et al., 2008).
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2.2.4 Raptor Presence
The use of flying raptors, typically hawks, in sites to control pigeon populations is a deterrent method used to discourage pigeons from remaining in an area with a natural predator (Oxley,
2013). The cost of a program involving visits with a raptor and trained handler varies greatly depending on the technician, with an approximate range from USD$1,000-2,000 weekly
(Wackernagel, 2009). At the University of South Africa’s Muckleneuk campus, the visual presence of raptors as a method to control pigeon populations was not effective long term, as they found no significant decrease in number of pigeons between scare treatments. The treatments were only successfully at modifying pigeon behaviour for short increments, whenever the raptor was present (Harris et al., 2020). TransLink, a public transportation service in the
Lower Mainland of BC, Canada, employed Raptor Ridge Birds of Prey’s peregrine falcons in a six-week long pilot project costing CAD$18,000 to disperse pigeons from SkyTrain stations
(Mangione, 2018). Overall, it was found that the pigeons returned to the stations once the falcons left the sites (Mangione, 2018).
2.3 Lethal Methods
Lethal methods include the use of Avitrol®, a chemical frightening agent, as well as culling through trapping, killing, and shooting. Avitrol® is marketed as a substance that invokes a nervous response in pigeons when ingested to signal other pigeons to relocate from treated sites
(Swindle, 2002), however numerous articles confirming its lethal effects in pigeons will be discussed. For this reason, Avitrol® will be considered a lethal method of control. Traditionally, the welfare of pest animals has been undervalued (Baker et al., 2016) however, opposition to
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lethal management methods is becoming widespread due to concerns regarding animal welfare, human safety and environmental impact (Beringer et al., 2002; Sharp & Saunders, 2011).
2.3.1 Avitrol®
Avitrol® bait consists of corn treated with 4-aminopyridine, a potassium channel blocker, and it affects the nervous system of pigeons (Swindle, 2002). The manufacturer claims birds who ingest the treated bait will react in a ‘strange manner’, typically mimicking a seizure, and that this reaction will be interpreted as distress in the remainder of the pigeon flock causing the birds to leave the site (Swindle, 2002). Stated on the manufacturer website, Avitrol® does not affect non-target species such as other birds or mammals, which they claim is confirmed by the U.S.
Fish and Wildlife Service (Swindle, 2002). The Pest Management Regulatory Agency of Canada released a Re-evaluation Decision in 2016 regarding 4-aminopyridine, granting continued registration of 4-aminopyridine for sale and use in Canada as a restricted product for those with appropriate licenses to use and distribute (Government of Canada, 2016). Avitrol® has been approved for use in the US since 1972 under the Environmental Protection Agency, although municipalities in both Canada and the US may choose to ban the substance (Macpherson, 2019).
For example, municipal bylaws in Halifax, Red Deer, New York and San Francisco ban the use of Avitrol® (Macpherson, 2019), and BC indirectly restricts its use by not issuing provincial permits.
Despite claims from the manufacturer that Avitrol® is not intended to be lethal, recent reports have shown otherwise. Living Sky Wildlife Rehabilitation Centre in Saskatoon, Canada has been treating pigeons admitted to their facility for poisoning from Avitrol®, with approximately half of the admitted animals dying (Macpherson, 2019). Recently in Ontario, a pest control company 19
was fired after administering Avitrol® to a pigeon population whereby residents witnessed birds walking in circles, falling out of trees, as well as convulsing and trembling before dying (Butler,
2020). Similarly, in Nova Scotia, birds have been arriving at The Hope for Wildlife
Rehabilitation Centre seemingly being poisoned, with a number of the pigeons dying that the centre attributes to Avitrol® (Thomas, 2020). Many residents in Ontario and Nova Scotia witnessing the effects of Avitrol® on pigeon populations expressed concern for the safety of their pets and children near the substance, as well as distress at witnessing what they claim to be inhumane suffering of animals who have ingested Avitrol® (Butler, 2020). Recently, four people including two building managers are facing felony animal cruelty charges for using Avitrol® to control pigeons at a building in downtown Pennsylvania that resulted in the death of over ten birds and violated regulations surrounding the use of Avitrol® (Guza & Tierney, 2021).
2.3.2 Culling
A common approach to managing wildlife and pest populations is culling to reduce the target population, which may produce immediate but short-lasting responses (Asa & Moresco, 2019).
Culling can include trapping followed by cervical dislocation, shooting, fumigants, and deliberately introduced disease with the intent of causing death in an animal (Oogjies, 1997). In pigeons specifically, due to their rapid reproduction rates, lethal methods rarely last as the remaining birds are able to quickly reproduce and replace population numbers to their previous levels (Macdonald, 2013). Lethal control is also typically labour intensive and costly
(Macdonald, 2013). Public opposition towards culling and lethal methods of pest control are often due to animal welfare concerns, and thus makes lethal methods increasingly socially unacceptable (Pelizzari, 2017). 20
2.4 Reproductive Control
Reproductive control in pigeons involves manual egg removal or the administration of avian contraceptive, OvoControl® P. Egg removal can include removing eggs from nests entirely or replacing viable eggs with dummy eggs (Jacquin et al., 2010). Contraceptive methods for controlling pigeon populations may be challenging to implement as it does not offer instant results to reduce population numbers, however members of the public are continually choosing to replace lethal techniques with more effective and humane contraceptive tools (Macdonald,
2013). Unlike most lethal methods of population control, reproductive control avoids large fluctuations in population cycles and favors stable population sizes which can reduce human- wildlife conflict (Bromley & Gese, 2001). Fertility control has also become a favoured option due to a shift in public attitudes away from acceptance of lethal methods (Oogjies, 1997; Reiter et al., 1999).
2.4.1 Pigeon Reproductive Biology
Feral pigeons are known to be remarkably prolific breeders and are sexually mature before they are one year old (Johnston & Janiga, 1995). With an average lifespan of 2.4 years in urban environments, they can produce five to six clutches annually with young birds departing as early as 25 days of age (Johnston, 1992). Feral pigeons breed in colonies with a general clutch size of two eggs and incubation lasts 18 days (Johnston & Janiga, 1995). The overall sex ratio for pigeons is 0.5 (Johnston & Janiga, 1995). Pigeons are monogamous and are assumed to have long-term fidelity between partners (Johnston & Janiga, 1995). Although pigeons can become sexually mature at six months old, young birds (<1 year) account for a very small fraction of the breeding population, and their breeding success is approximately 80% lower than adults 21
(Johnston & Janiga, 1995). The maximum age of reproduction is seven years (Haag-
Wackernagel, 1995), which signals senescence and a decline in reproductive ability (Johnston &
Janiga, 1995).
Findings by Kanojia & Shallu (2020) suggest that breeding seasons of feral pigeons are able to be extended throughout the year, outside of peak times (spring and summer), for those feral pigeons who did not lay eggs when humans were present or when there were unusual environmental conditions. The proportion of birds reproducing seasonally has clear geographical variation, with the length of the reproductive period tending to scale inversely to latitude
(Johnston & Janiga, 1995). These characteristics, generally rapid breeding and relative short lifespan in urban environments, enable contraceptive population management methods to potentially have a profound effect on pigeon populations.
2.4.2 Egg Removal
Egg removal is a technique of manipulating pigeon breeding attempts by either removing laid eggs entirely or replacing laid eggs with dummy eggs that will not form viable embryos and not result in hatchlings (Jacquin et al., 2010). To test the efficacy of egg removal as a population management tool, Jacquin and colleagues (2010) compared egg-laying cycles in pigeon houses between those exposed to egg removal and a control group. It was found that pigeons exposed to egg-laying removal had egg laying cycles that were shorter (four weeks) compared to the control group (11 weeks) (Jacquin et al., 2010). Jacquin and colleagues (2010) concluded that pigeons respond to egg removal by multiplying reproduction attempts, resulting in a decline of egg quality and female condition. It is important to note that in this research simply removing eggs
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without the use of dummy eggs does not have empirical evidence to suggest the same results would be obtained if dummy eggs were used (Jacquin et al., 2010).
2.4.3 OvoControl® P
OvoControl® P (Innolytics, LLC, Ranchero Santa Fe, CA, USEPA Registrations No. 80224-
1) is an avian contraceptive consisting of nicarbazin as the active ingredient. Nicarbazin is an equimolar complex consisting of 4,4′-dinitrocarbanilide (DNC) and 2-hydroxy-4,6- dimethylpyrimidine (HDP) (Yoder et al., 2006) and was originally used to control coccidiosis in broiler chicken feeds since the 1950s (Jones, 1990). One mechanism nicarbazin is thought to disrupt is the vitelline membrane in eggs allowing the yolk and albumen to mix, creating an environment where a viable embryo cannot form (Sherwood et al., 1956; Yoder et al., 2006;
Yoder et al., 2005). This effect on reproductive capacity was first considered for pigeon population control in the 1990s by an Italian veterinarian and health researchers (Pelizzari,
2017). Currently, nicarbazin is approved for population management in feral pigeons in Italy and
Spain, where it is registered as a veterinary drug, and in the US and Canada, where it is regulated as a pesticide (Pelizzari, 2017).
When nicarbazin is ingested by pigeons it dissociates into two constituent parts, DNC and
HDP which are chemically inactive; meaning there is no threat to secondary consumers (Yoder et al., 2006). Pigeons must have a specifically formulated bait as DNC particles can inhibit absorption through the intestinal wall (Rogers et al., 1983; Bynum et al., 2005; Yoder et al.,
2006), so pigeons must consume a constant concentration in order to effectively inhibit reproduction (Avery et al., 2008). Nicarbazin is cleared from the body once consumption ceases, meaning the effect on fertility is fully reversible (Massei & Cowan, 2014). This poses minimal 23
risk to predators and scavengers, but also requires that pigeons be treated with nicarbazin before and during the egg-laying period, as birds can recover in four to six days once ingestion of treated food has stopped (Yoder et al., 2006).
Pigeons must be habituated to feeding areas prior to administering OvoControl® P treatment and it is typically recommended that pigeons be fed plain maize kernels for a minimum of two weeks to ensure pigeons will consume feed in chosen areas (Innolytics, 2021). Regular corn feed can then be replaced with OvoControl® P; the manufacturer recommends one pound of
OvoControl® P for 80 birds daily. The feed can be provided manually in public spaces or parks or by automatic feeders placed on flat surfaces where daily access is not necessary. Population reduction rates as quoted by the manufacturer range from 30% to 50% (Innolytics, 2021) in the first year, with a continual decrease in populations for the following two to four years, before stabilizing at significantly lower population levels (Innolytics, 2021). Studies performed on pigeon populations using OvoControl® P and its efficacy will be further discussed in detail in
Chapter 3.
For contraception to be successful, it must be safe, effective and long-lasting but also have minimal impact on behaviour and social impacts of treated populations (Castle & Dean, 1996).
OvoControl® P has potential to fulfill these criteria, however OvoControl® P is licensed as a pesticide for use in Canada and the US which limits its use by private individuals. This designation may also lead to a misunderstanding among the public since a pesticide label may suggest that it is lethal and could generate opposition among people who would otherwise be supportive (Asa & Moresco, 2019). Furthermore, this designation also requires that the treatment be administered by Certified Pesticide Applicators, which requires hiring specialists or wildlife
24
managers to acquire training and certification, potentially compounding cost and additional barriers to companies offering this treatment (Asa & Moresco, 2019).
2.5 OvoControl® G
OvoControl® G is a formulation of nicarbazin intended to inhibit reproduction in Canadian geese, produced by the same manufacturer of OvoControl® P, Innolytics (Caudell et al., 2010).
To test the efficacy of OvoControl® G, Bynum and colleagues (2007) conducted a field efficacy trial in 2004 in Oregon, US with a total of four control groups and six treated groups for approximately six weeks. Ultimately it was found that there was a 93% increase in the percentage of nests at treated sites with 0% hatchability, as compared to nests with no eggs hatching at control sites (Bynum et al., 2007). The authors conclude that hatchability from treated sites as compared to control sites was reduced by 36%. Further, when OvoControl® G is administered by licensed, trained applicators immediately prior to and during the breeding season, OvoControl® G can be effective at reducing the number of goslings into resident
Canadian geese populations (Bynum et al., 2007). However, although treatment was considered effective, the authors also concluded that due to Canadian geese being a long-lived migratory species with a long breeding life, it is unlikely that reproductive control alone was likely to result in significant population decreases quickly enough to reduce conflicts between humans and resident Canadian geese (Bynum et al., 2007).
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2.6 Reproductive Control in Other Species
2.6.1 Introduction
As increasing concern for the welfare, safety and environmental impacts of conventional lethal methods of wildlife management reduce their acceptability, there is an increasing interest in using fertility control to manage wildlife (Massei & Cowan, 2014). Fertility control that is suitable for field applications should have the following characteristics: (a) have acceptable or no side-effects on animal physiology, welfare or behaviour; (b) be effective when administered in one dose; (c) render all or the majority of animals infertile for the duration of their potential reproductive life; (d) inhibit reproduction in at least one sex; (e) minimize interference with existing pregnancy or lactation; (f) be relatively inexpensive to produce and deliver; (g) have no effects on secondary consumers; (h) be administered through remote delivery; (i) be species- specific; and (j) be stable under a wide range of environmental conditions (Kirkpatrick & Turner,
1991; Massei & Fournier, 2012; Massei & Miller, 2013).
However, even contraception that fulfills these ideal conditions may be scrutinized for its use in free-ranging populations for the lack of control of immigrating and emigrating animals
(Malcolm, 2008). This may impact the fertility control being chosen to address human-wildlife conflict in field settings. By reviewing fertility control use in other species of animals that may be free ranging, we can infer potential efficacy of fertility control in free-ranging pigeons.
2.6.2 Reproductive Control in Urban Wildlife
Reviewing fertility control in other species of free-ranging urban wildlife, specifically cats and rats, may provide insight into the efficacy of fertility control in urban environments when animal populations are geographically unrestricted. 26
Two reproductive antigens, the Porcine Zona Pellucida (PZP) vaccine or a variant of gonadotropin-releasing hormone (GnRH) may be suitable for reproductive control in free- ranging cats. However, GnRH has found to be significantly more effective than PZP in cat populations due to its regulation of pituitary and gonadal hormone responses in both males and females (Benka & Levy, 2015). Currently, the efficacy of GnRH immunocontraceptive vaccine,
GonaCon®, has only been assessed for use in cats in laboratory settings (Benka & Levy, 2015).
Results from laboratory studies demonstrate positive results with 93% of vaccinated cats remaining infertile for the first year following vaccination, and 73%, 53% and 40% infertile for the following two, three, and four years respectively (Benka & Levy, 2015). However, studies in free-ranging urban populations are needed to assess the efficacy of this type of population management.
Fertility control in rats is available through the use of ContraPest®, a liquid bait that limits reproductive capacity in both male and female wild Norway and roof rats (Pyzyna et al., 2018).
With similar properties to OvoControl® P, ContraPest® must be consumed by rats regularly and has fully reversible effects (Pyzyna et al., 2018). Studies to test the efficacy of ContraPest® involved assessing free-ranging rats in an agricultural setting as well as an urban setting, and it was found that rats on farms decreased by an average of 46% the following 100 days from initial treatment (Pyzyna et al., 2018). In a complex urban environment, where property boundaries limited access to populations and foraging areas, ContraPest® reduced the seasonal population peak by 67% after 133 days of treatment (Pyzyna et al., 2018). The authors concluded that
ContraPest® is an effective tool to enhance long-term population control in rural, urban and agricultural environments (Pyzyna et al., 2018) however, it would be beneficial to assess effectiveness over longer periods of time to assess if successful outcomes are maintained. 27
2.6.3 Free-Ranging Wildlife
Fertility control in free-ranging wildlife populations typically involves the PZP vaccine or a variant of GnRH. To test the efficacy of PZP vaccine to control a small population of free- ranging elephants in the Makalali Conservancy, Limpopo Province, South Africa, 18 targeted females were provided the vaccine (Delsink et al., 2006). All of the treated females passed their intercalving interval of 56 months without giving birth and a growth rate of zero was maintained within this target group from August 2002 until 2006 (Delsink et al., 2006). The authors concluded that immunocontraception should be considered a viable means of population management as an alternative to long-term culling strategies in small populations of free-ranging elephants (Delsink et al., 2006).
Further, PZP vaccine was administered to 29 female suburban white-tailed deer (Odocoileus virginianus) in the fall of 1997 until spring of 1998 in a free-ranging population in Connecticut
(Walter et al., 2002). The authors concluded that treatment of approximately 70% of the suburban white-tailed deer population was possible and effective in managing the population, however the protocol was labour intensive, and a budget model estimated the cost of treatment to be approximately USD$1,128/ treated deer (Walter et al., 2002).
Fertility control involving variants of GnRH have also been studied in free-ranging elk, free- ranging cattle, as well as a GnRH agonist called deslorelin in free-ranging kangaroos. During the fall of 2002 to the spring of 2004, Powers and colleagues (2011) distributed fertility control in the form biodegradable implants containing GnRH agonist leuprolide to 17 free-ranging female elk that resided in Rocky Mountain National Park in Colorado, US. Initially, after treatment the pregnancy rate of the treated elk was 0% whereas it was 79% in the untreated elk (Powers et al.,
2011). However, the treatment was reversed the subsequent year and the pregnancy rate of the 28
treated females was 100%, concluding that controlling fertility in free-ranging elk populations is safe and effective, but practical implementation is limited by the need to provide treatment before breeding season annually (Powers et al., 2011).
Additionally, Massei and colleagues (2018) assessed the effectiveness of immuno- contraceptive vaccine GonaCon® on free-ranging feral cattle in Hong Kong by capturing and administering the vaccine or a control of saline solution to 60 female cattle. Those that received the treatment vaccine were given a booster dose 3-6 months later. It was found that the proportion of pregnant animals in the treatment group decreased from 76% at initial vaccination to 6% one year after vaccination compared to 67% and 57% respectively in the control group
(Massei et al., 2018). The authors concluded that GonaCon® is safe and effective in inducing infertility in feral cattle but that a booster dose is critical for maintaining infertility which requires access to the cattle for vaccination (Massei et al., 2018).
Further, to investigate the efficacy of fertility control in kangaroos in Victoria, Australia,
Wilson and colleagues (2013) distributed slow-release hormonal implants containing deslorelin to 53 free-ranging female kangaroos across three different study sites and monitored their reproductive success over the span of three years. Ultimately, the authors concluded that deslorelin implants reduced fertility in free-ranging kangaroos over three successive breeding seasons but that this treatment would only be practical to apply at sites where kangaroos could easily be captured as the treatment would need to be reapplied (Wilson et al., 2010).
2.6.4 Conclusions
Despite practical challenges with administering reproductive control to free-ranging populations of animals, there is an increased interest in wildlife population management that is 29
effective, safe and humane (Eisemann et al., 2013). The findings of the research conducted in
Chapter 3 contribute to the small body of literature in reproductive control of free-ranging populations of animals and provide insight into the challenges and practical considerations. As demonstrated by previous studies, testing the efficacy of reproductive control in free-ranging animals may provide a viable population management option but typically involves practical considerations that need to be addressed. As reproductive control increases in use for free ranging populations, such as in California where ContraPest® will be replacing second generation anticoagulant rodenticides (SGARs) (Governor of California, 2020), it will become imperative to understand practical limitations. As demonstrated by research evaluating the efficacy of fertility control in other species of urban wildlife and free-ranging species of animals, success is possible when using fertility control but is not without practical concerns or limitations such as cost, feasibility of multiple applications, and an easily accessible location.
2.7 Summary
There are significant efficacy and social license considerations for management methods of feral pigeon populations. For example, exclusion methods are popular for their perceived effect of removing populations quickly but have no actual impact on the size of populations and succeed only in moving pigeons to different sites, whilst being cost prohibitive at large scale sites (Macdonald, 2013). Lethal methods may work well initially, however, the population size typically returns due to the short and fast reproductive nature of pigeons (Pelizzari, 2017).
Reproductive control may be undesirable to those seeking immediate results and complete removal of pigeon populations (Macdonald, 2013), but has demonstrated success in other species with some practical considerations (Walter et al., 2002; Delsink et al., 2006; Wilson et al., 2010; 30
Powers et al., 2011; Massei et al., 2018; Pyzyna et al., 2018). The type of feral pigeon population management method chosen by businesses, institutions, or governments will likely reflect the desirable state of the populations; typically, whether a complete eradication of the population or the presence of a small, but manageable, population is desired. Achieving this state however must also consider humaneness, efficacy and practicality.
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Chapter 3: Humane Population Management of Rock Pigeons (Columba livia) using avian contraceptive OvoControl® P at various TransLink SkyTrain stations across the Lower Mainland of BC, Canada.
This chapter will review the methodology of the research conducted using avian contraceptive
OvoControl® P at TransLink SkyTrain stations in an attempt to achieve humane population management. To set the context for this research, a background on human-pigeon conflicts at
TransLink SkyTrain stations will be provided, followed by a review of previous studies using
OvoControl® P to control pigeon populations, and the methods used to assess the efficacy of
OvoControl® P at TransLink SkyTrain stations.
3.1 Introduction
TransLink is recognized as the authority to provide for transportation needs of communities in the Lower Mainland of southern BC, Canada. Founded in 1999, TransLink offers services through operating companies including Coast Mountain Bus Company, British Columbia Rapid
Transit Company Ltd (BCRTC), Metro Vancouver Transit Police and West Coast Express Ltd
(TransLink, 2021). For the purposes of this thesis only BCRTC, which operates SkyTrain stations, will be discussed in further detail. Originally launched in 1985, BCRTC operates two of three SkyTrain lines in Metro Vancouver: the Expo Line and the Millennium Line (TransLink,
2021). The Expo and Millennium SkyTrain lines connect downtown Vancouver to the neighbouring cities of Burnaby, New Westminster, Coquitlam, Port Moody and Surrey
(TransLink, 2021).
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SkyTrain first became operational in 1986 with the Expo Line which was followed by the
Millennium line in 2002 (TransLink, 2021). Currently, there are a total of 17 operational stations on these lines with the most recent additions constructed in 2016, and there are intentions to expand operations (TransLink, 2021) as shown in Figure 1. The Expo and Millennium lines run mostly on elevated guideways and operate a maximum speed of 80 km/h (TransLink, 2021). It is estimated that approximately 350,000 passengers ride SkyTrains daily on weekdays, and for some, SkyTrain may be their main transportation method (TransLink, 2021). Trains are conducted through automatic train operation, protection, and regulation and they have a dual processor computer that controls propulsion, braking, direction, door operation, and monitors speed and critical faults (TransLink, 2021).
Figure 1. TransLink SkyTrain station and service map. (TransLink, 2021). 33
The layouts of SkyTrain stations may vary at each station, but stations typically provide elevated roosting areas for pigeons and have large open spaces and ceilings to allow trains access to the stations, which also enables pigeons to enter freely. A sample of station layout is provided in Figure 2, displaying a train entering 22nd Street SkyTrain station. This man-made habitat for pigeons is primed for human-wildlife conflict. SkyTrain stations typically have neighbouring restaurants or dumpsters that provide food to pigeons. Further, some commuters and local residents feed the pigeons daily, despite efforts from the British Columbia Society for the
Prevention of Cruelty to Animals (BC SPCA) to display signage discouraging the feeding of pigeons. These factors combined provide a thriving environment for pigeon populations.
Figure 2. Train entering 22nd Street SkyTrain station (Mcmanus, 2020).
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3.1.1 Pigeon Abundance at TransLink SkyTrain Stations
An abundance of pigeons at SkyTrain stations can cause human-wildlife conflict through excrement, track alarm triggers, and an unpleasant environment for customers. Pigeon populations can accumulate excrement at SkyTrain stations, which is unfavourable for customers due to the potential disease vector (Pellizzari, 2017), and additional maintenance costs for
TransLink as the need to remove excrement is ongoing (Nijjar, 2020). Further, the presence of the pigeons at stations may be unfavourable for customers who consider pigeons to be unsanitary pests and may submit complaints to TransLink about their presence in SkyTrain stations (Nijjar,
2020).
Pigeons may also fly through SkyTrain tracks which trigger track alarms that halt the train due to the automated system that is unable to distinguish pigeons from other objects that may fall through the guard rails of the train tracks (Nijjar, 2020). Typically, these incidents require staff members to investigate the cause of the alarm which may halt service through the station and inconvenience customers, while being an additional cost to TransLink (Nijjar, 2020). These incidents may also be dangerous for customers riding the train as track alarms cause the train to stop abruptly and may cause riders to lose their balance (Nijjar, 2020). In 2015, a bird nest ignited on the SkyTrain station tracks at Main Street station and damaged a communications cable along the Expo Line that required workers to work through the night to repair (Petralba,
2015). TransLink advised customers to make alternative travel plans for the next day and provided a shuttle bus between Joyce-Collingwood station and Waterfront station, but warned against heavy crowds and delays (Petralba, 2015). Due to the inconvenience, TransLink offered free service to customers on all buses, the Seabus, Westcoast Express train and all SkyTrain routes for that day (Crawford, 2015). 35
TransLink SkyTrain has employed numerous methods to remove pigeon populations from their stations including netting, spiking, raptor presence, and physical lethal removal, but none have removed pigeon populations entirely or had lasting effects on the pigeon populations at any
SkyTrain station (Nijjar, 2020). Terminix has held the pest control contract with TransLink
SkyTrain for the past three to four years and currently still deploys netting and spiking as exclusion methods at SkyTrain stations (Muxlox, 2019). Netting may be ineffective due to the inability to completely exclude pigeons due to the front entrances for customers and gaps for the train to enter the station (Muxlox, 2019). Initially, spiking may have some effect in excluding pigeons from targeted areas at TransLink SkyTrain stations. However, birds have been observed to make nests in spikes with a buildup of excrement and debris, removing any exclusionary capacity as pigeons are able to comfortably perch on the spikes (Muxlox, 2019). The costs associated with spiking and netting one SkyTrain station will vary depending on the size and extent of coverage but can potentially reach CAD$20,000 to apply netting to one station
(Muxlox, 2019).
As previously mentioned, the presence of raptors did not have a lasting effect at TransLink
SkyTrain stations (Mangione, 2018) and there exists the potential for public disapproval of lethal control methods (Pelizzarri, 2017). In order to avoid humaneness concerns and public opposition to lethal control of pigeon populations, OvoControl® P was recommended to TransLink as a humane solution to control pigeon populations by Dr. Sara Dubois of the BC SPCA, due to claims that it reduces pigeon populations by 50% after the first year of treatment (Innolytics,
2021).
Given the novelty of OvoControl® P not previously being used by Terminix (Muxlox, 2019) and only recently being approved for use in Canada as of April 2018 (Innolytics, 2021), proof of 36
concept was required for the project to be approved by TransLink. To obtain approval for the project from TransLink, an initial station, VCC-Clark, was selected to serve as a pilot site May
2019 to September 2019 due to the known pigeon population and excessive amount of track alarm triggers observed at this station. Due to ease of implementation of the feeders, and video footage confirming the pigeons consuming the bait daily at VCC-Clark, expansion of the project was approved in September 2019 to eight stations. To predict the potential outcomes of using
OvoControl® P at TransLink SkyTrain stations, previous studies using OvoControl® P were reviewed for their outcomes.
3.2 Results of OvoControl® P Use in Other Studies
There are few independent studies evaluating the efficacy of OvoControl® P in the field, however, three studies evaluate the use of Ovistop®, the European formulation of the nicarbazin avian contraceptive. The first was conducted in closed aviaries to simulate results in two Italian cities Lucca and Venice (Giunchi et al., 2007), the second in the Italian City of Genoa (Albonetti et al., 2015), and the third in the city of Barcelona, Spain (Senar et al., 2021). Additionally, researchers at Texas Tech University have assessed managing pigeon populations on campus using a range of methods such as netting, spiking, and screening in addition to OvoControl® P
(Stukenholtz et al., 2019). Further, studies conducted by the manufacturer of OvoControl® P,
Innolytics, can be reviewed with the understanding that successful results may influence the marketing and sales of the product (Innolytics, 2021).
Giunchi and colleagues (2007) tested the efficacy of nicarbazin on groups of paired feral pigeons maintained in open aviaries. They simulated the possible effects of nicarbazin on a hypothetical pigeon population modelled in two Italian cities, Lucca and Venice, by taking into 37
account the reproductive output recorded for the two cities. Breeding was assumed to occur year- round in both cities due to the climate and results were simulated by means of population viability analysis (Giunchi et al., 2007). Giunchi and colleagues (2007) estimated population declines using mathematical models in different scenarios where consumption of nicarbazin was inconsistent and low, or consistent and high, and estimated a relatively rapid decline in pigeon populations after the first year of consumption, a range from 18% to 41% depending on the consumption scenario. At the end of five years, reduction in pigeon populations was estimated within a range of 50% to 90% depending on the degrees of consumption (Giunchi et al., 2007).
The authors concluded that variability in the treatment outcome is likely due to individual susceptibility to the treatment and the daily consumption rate of nicarbazin, however in uncontrolled field settings, factors such as food availability or nesting sites may also affect results (Giunchi et al., 2007).
Albonetti and colleagues (2015) evaluated the use of Ovistop® over the span of eight years
(2005-2011) in the city of Genoa, Italy by observing four non-migratory feral pigeon colonies with three treatment groups and one control group (Albonetti et al., 2015). The treated groups received 10 grams of Ovistop® five days each week and the control stations were provided a placebo (Albonetti et al., 2015). In the pigeon colonies treated with Ovistop®, there was an initial increase in the population called the ‘magnet effect’ which occurred for an unspecified amount of time, a reduction observed over the following four years (35% to 45%), and a further decrease in the subsequent four years (65% to 70%). This was observed across all three of the treated stations, compared to an overall unstable trend at the control station (Albonetti et al.,
2015). The authors state that given the results, and that no external or exceptional factors were noted, Ovistop® seemed effective in reducing treated pigeon populations (Albonetti et al., 2015). 38
The third study tested the efficacy of Ovistop® in the city of Barcelona, Spain by setting 23 stations to dispense Ovistop® throughout Barcelona and ten stations with untreated corn to serve as controls (Senar et al., 2021). To evaluate pigeon population numbers, censuses were conducted within a 200-metre radius of the feeder sites before and after one year of the treatment
(Senar et al., 2021). The researchers found that feral pigeon density did not change after one year at treatment sites and population sizes increased by 10% at control sites. They concluded that the feral pigeon population overall rose by 10% by the end of the study (Senar et al., 2021). Due to these findings, Senar and colleagues (2021) advised against the use of Ovistop® as a pigeon control method in large cities. However, it is important to note that Senar and colleagues (2021) also stated that pigeon density in 200-metre circles around each feeder did not correlate with counts at the feeders, suggesting that these specific population count methods were poor density estimators. They suggest that the assumption that a reduction over time in bird counts at experimental feeders reflected a reduction in population size was likely wrong and rather that the reduction of populations at feeders is attributed to poor palatability of Ovistop®, given the formulation of feed selected for the study (Senar et al., 2021).
Stukenholtz and colleagues (2019) conducted a case study at Texas Tech University to test the efficacy of various pigeon population management methods including netting, spiking, the use of screens, and OvoControl® P. Although difficult to determine the effects of OvoControl® P alone due to the presence of other management methods, the authors preliminary results suggest a reduction in pigeon populations next to buildings where OvoControl® P is being dispensed, but full analyses are not available (Stukenholtz et al., 2019). Ultimately, the authors conclude that it is important to include multiple management methods that remove resources from pigeon
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populations as well as decreasing the number of offspring through the use of OvoControl® P to successfully decrease populations (Stukenholtz et al., 2019).
A study conducted by the manufacturers of OvoControl® P in San Diego, US initially started with 150 birds at both a treated site and a control site and found that the treated site decreased in population size by 53% in the first year of treatment and 88% after the first 28 months of treatment (MacDonald & Wolf, 2009). Similarly, an Italian pest control company conducted a study testing the efficacy of Ovistop® in the historic city of Rimini, Italy and reported a 48% decline in pigeon populations after 14 months of treatment (Freedom Co., Ranchio di Sarsina,
Italy, 2007) however, it is unclear if this study was conducted in partnership with the manufacturer.
3.2.1 Study Predictions
Considering the findings of previous studies using nicarbazin, either OvoControl® P or
Ovistop®, the predicted findings of using OvoControl® P at TransLink SkyTrain stations is a decline or no change in pigeon populations in the first year at treatment stations, and an increase or no change in the pigeon populations at stations serving as control sites with cracked corn as treatment. This is largely based on the findings of Giunchi and colleagues (2007) and Albonetti and colleagues (2015), as the experimental sites are more segregated and may provide clearer study site boundaries than the study sites in research conducted by Senar and colleagues (2021).
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3.3 Goals of Research Project
The goals of the TransLink SkyTrain research are to determine if OvoControl® P can effectively manage pigeon populations by reducing pigeon populations at treated stations, thus reducing track alarm trigger events and excrement volume and maintenance.
To be considered effective for the long-term purposes of TransLink SkyTrain station management, OvoControl® P must be easy to maintain and dispense, be cost effective, effectively reduce pigeon populations, excrement complaints, and the number of track alarm triggers, and be feasible to establish at SkyTrain stations to ensure no theft, damage or the attraction of additional pests (Muxlox, 2020).
3.4 Methods
To test the efficacy of OvoControl® P to reduce pigeon populations and track alarm triggers at TransLink SkyTrain stations, eight stations were chosen to serve as study sites with four stations dispensing OvoControl® P and four control stations dispensing cracked corn. A summer student at the University of British Columbia previously created a project proposal based on population estimates in 2018 at different stations to allow TransLink to assess potential need for pigeon control at stations with higher population figures (Roberts, 2018). Eight stations overall were selected to meet cost restrictions due to equipment and monitoring, as well as the availability of stations that fit criteria to be included in the study. All stations considered for selection in the study were required to meet the following criteria: the presence of a pigeon population, an area to set up feeder that is not accessible to the public, an area to set up feeder that is accessible to graduate student and pest control technicians, and an area to set up feeder that does not pose a safety risk to the general public. The four stations chosen to dispense 41
OvoControl® P were randomly selected from within the eight stations selected by TransLink by a random number generator. An initial station, VCC-Clark, was set up to dispense cracked corn to test equipment and monitoring technique as a pilot for four months (August 2019 to
November 2019) before it became part of the treatment sites. This time period was required to receive necessary approval from TransLink to establish additional study sites but could potentially skew data as other stations did not dispense cracked corn for the same time period.
Stations were monitored for the duration of one year from March 15, 2020 to March 15, 2021.
Exceptions to this include Lafarge Lake station that was moved from Lougheed station due to rat infestation, and VCC-Clark station that was monitored for a different time period. Lafarge Lake station was monitored from August 13, 2020 to March 15, 2021. VCC-Clark station was monitored from January 8, 2020 to January 13, 2021 due to theft that ended monitoring before
March 15, 2021. As previous studies assessing the efficacy of OvoControl® P collected data for one year (Senar et al., 2021) and over the span of multiple years (Albonetti et al., 2015), the duration of one year of data collection was selected to assess the claims that OvoControl® P can reduce populations by 50% in the first year of use (Innolytics, 2021).
Each station was monitored using an automatic infrared digital trail camera (Moultrie A-900i
Digital Infrared Camera, MCG-14002) pointed at the feeding sites to provide pigeon population estimates and to ensure pigeons were ingesting either the OvoControl® P or the cracked corn.
Camera locations were chosen to ensure cameras were not visible to those passing by to minimize theft, therefore, distance from cameras to the feeders varied. OvoControl® P or cracked corn was dispensed from the Moultrie Deer Feeder Elite II Tripod feeder. Four stations received the treatment: VCC-Clark, Renfrew, Stadium-Chinatown, and Metrotown; and four stations received the control: Surrey Central, Joyce-Collingwood, Lafarge Lake, and 22nd Street 42
(Table 1). Joyce-Collingwood station was previously Braid station but was relocated due to recurring theft, although this did not affect the enrolment date of this station. 22nd Street Station was previously Holdom Station but was relocated due to an infestation of crows that prevented pigeons from accessing the feeder, although this did not affect the enrolment date. VCC-Clark enrolment ended prior to March 15, 2021 due to theft that resulted in damage at the station, but data was collected at this station for a whole year.
Table 1. Information on Eight Enrolled SkyTrain Stations
Stations Treatment Feeder Placement Enrolment Dates
22nd Street Control Roof March 15, 2020
Joyce Collingwood Control Roof March 15, 2020
Lafarge Lake Control Substation Roof August 12, 2020
Metrotown OvoControl® P Substation Roof March 15, 2020
Renfrew OvoControl® P Ground Level March 15, 2020
Stadium-Chinatown OvoControl® P Roof March 15, 2020
Surrey Central Control Roof March 15, 2020
VCC-Clark OvoControl® P Ground Level January 8, 2020
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3.4.1 Data Collection
Stations that were selected to dispense OvoControl® P initially dispensed cracked corn for a minimum of two weeks, referred to as the baiting period, as per Innolytics recommendation for best practices when using OvoControl® P to habituate birds to the feeding time and using the feeders (Innolytics, 2021). Figure 3 displays the visual characteristics of OvoControl® P
(Innolytics, 2021).
Figure 3. Visual sample of OvoControl® P (Innolytics, 2021)
The baiting period was prior to enrolment dates of January 8, 2020, March 15, 2020, and
August 12, 2020 and was included in the final analysis as the ‘Before’ period, referring to before treatment. Feeders were programmed to dispense treatments at 07:00 daily and pigeon populations were monitored through automatic infrared digital trail cameras from 07:00-12:00 daily to capture pigeon activity and populations present around feeding time. This time period was selected as pigeons typically feed in the morning (Johnston & Janiga, 1995) and to ensure pigeons were ingesting OvoControl® P before alternative human foods were available to them throughout the day, as this could deter them from consuming the required daily amount of
OvoControl® P. Further, it is estimated that once baited, pigeons consume the dispensed
OvoControl® P in three to five minutes (Innolytics, 2021). Each feeder is estimated to 44
accommodate up to 150 birds and the amount of OvoControl® P dispensed daily was calculated using Innolytics recommendation of 1 pound for every 80 birds or 5 grams per bird per day, which accounts for roughly 15% of the pigeons’ dry matter intake (Innolytics, 2021).
Study sites were serviced by Terminix, the pest control company hired by TransLink to service their Lower Mainland operations. Every two weeks a Terminix technician changed 32GB
SD cards in the trail cameras, replaced depleted AA batteries and refilled either cracked corn or
OvoControl® P in feeders. Maintenance by Terminix was necessary as OvoControl® P must only be handled by a licensed pest control applicator (British Columbia, 2021) in addition to many feeder sites being difficult to access and required the use of a ladder. The cost of maintenance and product through Terminix for each station dispensing OvoControl® P is approximately CAD$750 monthly and the cost of each station dispensing cracked corn is approximately CAD$350 monthly (Muxlox, 2020). Population estimates for each station were made from video footage obtained during the baiting period.
Figure 4 displays a visual sample of the experimental set up with (A.) referring to the
Moultrie Deer Feeder Elite II Tripod feeder dispensing either cracked corn or OvoControl® P and (B.) referring to the automatic infrared digital trail camera (Moultrie A-900i Digital Infrared
Camera, MCG-14002) on a tripod to capture images.
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A.
B.
Figure 4. Sample experimental set up of camera and feeder
3.4.2 Pigeon Population Video Monitoring
Daily pigeon counts at each station were conducted by noting the largest group of pigeons seen in 15 second video clips between 07:00 and 12:00. Cameras were set to run continuously and were triggered to turn on by movement and capture video for the duration of 15 seconds.
Placement of the cameras considered minimizing theft, camera angles that would not capture members of the public, and camera angles that could provide the most expansive view of the feeder and surrounding areas. As each station had varying layouts, each camera was placed in a different location relative to the feeder to fulfill the previous considerations. As it is not possible to count the entire population of pigeons present at SkyTrain stations, sampling was employed as a means to estimate the population (Elzinga et al., 2001). To minimize non-sampling error, it is important to ensure the sampling unit is conducive to the type of measurement selected, so there 46
will be consistency in counts or measurements when conducted by different people, and that data forms are simple and easy to use (Elzinga et al., 2001). To fulfill the criteria of minimizing non- sampling error and to streamline the monitoring process for reproducibility for other entities that would like to implement and monitor the efficacy of OvoControl® P, the following monitoring methodology was conducted. The 32GB SD cards containing footage of pigeon activity at
SkyTrain stations would be collected from Terminix biweekly and the videos were then sorted by date. Only footage between 07:00 and 12:00 would be reviewed due to the baiting of pigeons to the feeder dispensing feed at 07:00 and feasibility of footage review. Each clip would be paused at the frame with the most pigeons present in the frame and then pigeons would be counted. To be counted as one sampling unit, at least 50% of the animal needed to be in frame to ensure accuracy in identification (Elzinga et al., 2001). Figure 5 displays a sample of a still frame that could be counted for analysis. In this Figure, four pigeons would be counted as the population for this clip to be recorded.
Figure 5. Sample still frame from video footage
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A sample of a video monitoring sheet is shown in Figure 6 with the name of the station and the dates at the top of the sheet and subsequent pigeon counts in frames underneath each date.
The largest number of pigeons seen in a clip for the given day is highlighted, and the total number of pigeons observed for the date is totaled at the bottom, as well as the total number of clips observed between 07:00 and 12:00 for the given date. A daily value that expresses the number of clips, total number of pigeons, and largest grouping seen from 07:00 to 12:00 is provided at the bottom of the page shown in Figure 6. It is acknowledged that it is not possible that every animal present at the station would be captured in the frame of the camera. Please note that monitoring was typically recorded free hand in a notebook in the same format for ease of observing video.
Figure 6. Sample video monitoring sheet
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Once data was recorded with daily values, the data would be added to an Excel sheet for each station, organized for ease of conducting statistical analysis as well as containing notes of other species observed in the video clips for interest as shown in Figure 7. This allows for the isolation for the measurement of interest, whether it be the number of times the camera recorded video, the total number of pigeons observed for that date, or the largest group size observed for that date.
Figure 7. Sample data sheet for Surrey Central station
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3.4.3 Track Alarm Triggers
Secondary data from TransLink was also used in assessing pigeon activity at stations. Track alarms are triggered when an item, person or animal falls within a distinguished region of
SkyTrain tracks that are past the guardrails at each station. Track alarms are investigated by staff and categorized accordingly, track alarms categorized as ‘Animal’ or ‘Unknown’ are included in the study. Track alarms may have accompanying notes specifying the species of animal that caused the alarm, but in many incidents, this information is unknown. Data from each station on triggered alarms was obtained from BCRTC between May 2018 (earliest date of available data) and March 2021. A sample of track alarm trigger data is provided in Figure 8.
Figure 8. Sample track alarm trigger data for December 2019
Data is filtered for stations included in the study and sorted by year and month. Values provided to the right of the graph account for minutes of delay associated with each department
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listed. Any additional notes that were included in the data would appear next to these values. If no alarm was recorded on a specific day in a specific station, it was assumed there was no alarm on that day. The analysis of results will be discussed in Chapter 4.
Initially, data regarding customer complaints about pigeon presence at TransLink SkyTrain stations, data on the amount of excrement at each station, and data regarding the extent of daily cleaning involving pigeons at stations was included in the study at request from TransLink.
However, due to an inability to obtain data from various departments and data not being categorized in a way that would be relevant to the study, this data was not included in the study.
3.4.4 Analysis
All analysis were conducted using R version 4.0.4 (R Core Team, 2015). After descriptive analyses were obtained, the association between station and the number of pigeons observed
(maximum number in a group, and total number), as well as the association between station and the number of daily track alarms were assessed a zero-inflated mixed regression model, adjusted for day as random effect (Magnusson et al., 2020). Briefly, it is a two-component model with a count component and a zero component that models the excess zero counts. The model was then used to generate the marginal effect of stations for these outcomes (Lüdecke et al., 2021).
The association between daily number of track alarms and the number of observed pigeons each day (maximum number in a group and total number) was evaluated using a zero-inflated mixed regression model, adjusted for station and day as random effects.
Finally, the number of pigeons observed before and after the introduction of treatment was compared between stations receiving OvoControl® P and stations with cracked corn as an interaction in a zero-inflated mixed regression model, adjusted for station and day as random 51
effects. The station Lafarge Lake was removed from these analyses as there was no data prior to the treatment and the ‘Before’ and ‘After’ dates for VCC-Clark station were adjusted. The
“Before” period started on November 15, 2019 and ended on March 15, 2020 (January 8, 2020 for VCC-Clark), when treatment was introduced. The “After” period started on April 15, 2020
(February 8, 2020 for VCC-Clark), as it would be expected at least a month would be necessary for the treatment to have an effect and ended on March 17, 2021 (January 13, 2021 for VCC-
Clark). The data from March 15, 2020 to April 15, 2020 (January 8, 2021 to February 8, 2021 for
VCC-Clark) was removed as it was considered a transition period (nobservations = 217, from 62 days and 7 stations). The number of observed pigeons before and after the introduction of the treatment was compared between treatment groups as an interaction using a mixed linear regression model with date and station as random intercepts.
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Chapter 4: Results
The aim of Chapter 4 is to provide results of the experimental research and compare to results in previous studies using OvoControl® P to manage pigeon populations. The strengths and limitations of the research conducted will also be discussed, followed by potential applications of the findings and recommendations for areas of future research.
4.1 Results
A total of 3,218 observations were obtained from November 15, 2019 to March 17, 2021. The data came from eight SkyTrain stations and was available for 489 days. Raw data is presented in
Figure 9 displaying both the maximum number of pigeons observed at one time in the day (light- colored line) and the total number of pigeons observed in one day (dark-colored line). Missing data points in Figure 9 can be attributed to a variety of reasons including theft, equipment malfunction, or station changes caused by an increase in rats from feed being dispensed as previously discussed in Chapter 3.
The maximum number of pigeons observed per day per station varied between 0 and 57
(median = 14, mean = 15.0, SD = 12.4). It is important to note the disparity in pigeon population numbers, for example in Stadium-Chinatown where the total number of pigeons observed in day between 07:00 – 12:00 exceeds 750 birds while at VCC-Clark the number of birds does not exceed 50 which may have an impact on analysis.
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Figure 9. Maximum number of pigeons seen at one time in a day (light-color line) and total number of pigeons seen in a day (dark-color line) in eight SkyTrain stations in Vancouver
(Canada). Four stations (Renfrew, Stadium-Chinatown, VCC-Clark, and Metrotown) were experimental sites dispensing OvoControl® P, and four others (22nd Street, Surrey Central,
Lafarge Lake, and Joyce Collingwood) were control sites dispensing cracked corn.
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4.1.1 Treatment and Total Number of Pigeons
Associations between treatment type and the total number of pigeons observed each day at each station between 07:00-12:00 were assessed. Figure 10 depicts the treatment types, either cracked corn or OvoControl® P, and changes in the total number of pigeons observed ‘Before’ treatment and ‘After’ treatment (P = 0.01). Overall stations treated with cracked corn had a lower number of total pigeons in the ‘Before’ period and increased in the ‘After’ period while stations treated with OvoControl® P did not statistically increase from the ‘Before’ period to the ‘After’ period.
Figure 10. Predicted total number of pigeons observed in a day (± 95% confidence intervals) in seven SkyTrain stations in Vancouver (Canada), before and after the addition of treatment. Four stations (Renfrew, Stadium-Chinatown, VCC-Clark, and Metrotown) were experimental sites dispensing OvoControl® P, and three others (22nd Street, Surrey Central, and Joyce
Collingwood) were control sites dispensing cracked corn. Predicted values were obtained from a
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zero-inflated mixed effect model including the interaction between treatment and time-period
(before or after treatment), and the station and date as random effects (nobservations = 2,784 from
483 days and 7 stations).
Observed values of the total number of pigeons between 07:00-12:00 at each station daily are displayed in Figure 11. It is important to note the small total number of pigeons observed in stations dispensing cracked corn at the initial stage of treatment (April 2020) compared to
OvoControl® P which may have an impact on analysis.
Figure 11. Total number of pigeons observed daily before and after the addition of treatment
(April 2020) in eight SkyTrain stations in Vancouver (Canada). In four stations (VCC-Clark,
Renfrew, Stadium-Chinatown, and Metrotown) OvoControl® P was dispensed and in the four 56
others (Surrey Central, Lafarge Lake, Joyce-Collingwood, and 22nd Street) cracked corn was dispensed (nobservations = 3,007 from 458 days and 8 stations).
4.1.2 Treatment and Maximum Number of Pigeons
Associations between treatment type and the maximum number of pigeons observed at one time between 07:00-12:00 at each station daily was also assessed and results were similar to those comparing treatment type and the total number of pigeons observed each day. Figure 12 depicts the treatment types, either cracked corn or OvoControl® P, and changes in the maximum number of pigeons observed at one time each day ‘Before’ treatment and ‘After’ treatment (P =
0.01). Overall stations treated with cracked corn had a lower number of maximum pigeons in the
‘Before’ period and increased in the ‘After’ period while stations treated with OvoControl® P did not statistically increase from the ‘Before’ period to the ‘After’ period.
Figure 12. Predicted maximum number of pigeons observed in a day (± 95% confidence intervals) in seven SkyTrain stations in Vancouver (Canada), before and after the addition of 57
treatment. Four stations (Renfrew, Stadium-Chinatown, VCC-Clark, and Metrotown) were experimental sites dispensing OvoControl® P, and three others (22nd Street, Surrey Central, and
Joyce Collingwood) were control sites dispensing cracked corn. Predicted values were obtained from a zero-inflated mixed effect model including the interaction between treatment and time- period (before or after treatment), and the station and date as random effects (nobservations = 2,784 from 483 days and 7 stations).
Observed values of the maximum number of pigeons observed at one time between 07:00-
12:00 at each station daily are displayed in Figure 13. It is important to note the smaller maximum number of pigeons observed at one time in stations dispensing cracked corn at the initial stage of treatment (April 2020) compared to OvoControl® P which may have an impact on analysis.
Although neither analysis is perfect, either analyzing the maximum number of pigeons seen in one day at one time or analyzing the total number of pigeons observed at a station between
07:00-12:00, both provide similar results. Stations dispensing cracked corn increased in both their total number of pigeons observed each day from 07:00-12:00 and their maximum number of pigeons seen at one time each day between 07:00-12:00. Stations dispensing OvoControl® P did not change in either the total number of pigeons observed each day from 07:00-12:00 or the maximum number of pigeons observed at one time each day from 07:00-12:00.
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Figure 13. Maximum number of pigeons observed daily before and after the addition of treatment (April 2020) in eight SkyTrain stations in Vancouver (Canada). In four stations (VCC-
Clark, Renfrew, Stadium-Chinatown, and Metrotown) OvoControl® P was dispensed and in the four others (Surrey Central, Lafarge Lake, Joyce Collingwood, and 22nd Street) cracked corn was dispensed (nobservations = 3,007 from 458 days).
4.1.3 Track Alarm Trigger Results
The number of daily track alarms varied between 0 and 6 (median = 0, mean = 0.3, SD = 0.5).
The number of daily track alarms and maximum number of pigeons observed at one time between 07:00-12:00 varied by station (zero and count components: P<0.01). The relationship between the maximum number of pigeons observed at one time and track alarm counts showed 59
that more observed pigeons at a station on a day increased the odds of having no alarm, but there was no increased rate of higher counts if more pigeons were observed (Figure 14). This result was the same when comparing the total number of pigeons observed daily between 07:00-12:00 and track alarm counts. Figure 15 displays the observed maximum number of pigeons seen at one time between 07:00-12:00 daily (light-color line) with the number of track alarms (dots) with higher number of track alarms observed on days with smaller maximum number of pigeons seen at one time between 07:00-12:00.
Figure 14. Predicted change in the number of daily alarms according to the maximum number of pigeons observed at one time in a station (regression line ±95% confidence intervals), superposed to the observed data (points) in eight SkyTrain stations in Vancouver (Canada) from
November 15, 2019 until February 28, 2021. The association was obtained from a zero-inflated
60
mixed effect model including station and date as random effects (nobservations = 3,099 from 472 days).
Figure 15. Maximum number of pigeons seen at one time in a day (light-color line) and number of alarms in a day (points) in eight SkyTrain Stations in Vancouver (Canada). Four stations
61
(Renfrew, Stadium-Chinatown, VCC-Clark, and Metrotown) were experimental sites dispensing
OvoControl® P. Four stations (22nd Street, Surrey Central, Lafarge Lake, and Joyce-
Collingwood) were control sites dispensing cracked corn.
Although a statistically significant difference was observed for the association between track alarm triggers and both the total number of pigeons and the maximum number of pigeons observed at one time between 07:00-12:00, there was no significant difference between treatment types, either OvoControl® P or cracked corn, and track alarm triggers as shown in Figure 16.
Figure 16. Predicted number of daily alarms (±95% confidence intervals) in eight SkyTrain stations in Vancouver (Canada), before and after the addition of treatment (April 2020). In four stations (VCC-Clark, Renfrew, Stadium-Chinatown, and Metrotown) OvoControl® P was dispensed and in the four others (Surrey Central, Lafarge Lake, Joyce-Collingwood, and 22nd
Street) cracked corn was dispensed. Predicted values were obtained from a zero-inflated mixed 62
effect model including the interaction between treatment and time-period (before or after treatment), and the station and date as random effects (nobservation = 2,888 from 441 days and 8 stations).
4.2 Discussion
Overall, stations that dispensed cracked corn were found to initially have low numbers of total pigeons observed in the ‘Before’ period and increased ‘After’ treatment. Stations that dispensed
OvoControl® P did not change from the ‘Before’ period and the ‘After’ period. A small number of treatment groups can contribute to difficulty achieving significance in addition to large differences in the total number of observed pigeons at different stations. For example, a change in a station with 700 total pigeons observed daily (e.g., Stadium-Chinatown) might have a different impact than a change in pigeons at a station with 50 total pigeons observed daily (e.g.,
VCC-Clark). Further, there was a small number of pigeons in the ‘Before’ phase of analysis as bird populations tended to increase when they became baited to the feeding stations which may have influenced results comparing the ‘Before’ and ‘After’ periods. As it is possible that not all pigeons present at a station were captured on camera, some pigeons may not have ingested the treatment.
As feral pigeons typically have a lifespan in urban conditions of 2-4 years (Johnston & Janiga,
1995), it is not surprising that the groups treated with OvoControl® P did not see a significant change in observed pigeons. It is possible that these birds may not be reproducing, but a decline in their populations may take longer to observe due to their lifespans. However, the result that there was no increase at treated stations despite daily feeding, and an increase at control stations aligns with our predictions. Further, the result of increased odds of having no track alarm if more 63
pigeons are present was unexpected and may be explained by observing where pigeons are choosing to roost and nest. This may have a greater effect on track alarm triggers rather than the group size of the pigeons. Currently, there is only literature to suggest pigeons remain relatively close to their roosting and nesting habitats (Rose et al., 2006) but no studies assessing the effect of moving food sources short distances to influence nesting and roosting sites. Inquiry into whether the placement of the feeders at locations a farther from SkyTrain tracks would offer further understanding, as it could potentially aide in reducing track alarm triggers by encouraging pigeons to source food in alternative areas and to nest and roost in these locations. Further, as all track alarm triggers were included in analysis as it is not always possible to determine which alarms are caused by pigeons, it may be possible that alarms not caused by pigeons influenced the results.
Currently our results align with those found by Senar and colleagues (2021) who found an increase in pigeon populations at control sites dispensing cracked corn and no change in stations dispensing Ovistop® in the city of Barcelona, Spain. However, other studies have found population declines over longer time periods (Albonetti et al., 2015), therefore it is recommended that TransLink continue to apply treatment and monitor over longer periods, and perhaps attempt moving the feeders to locations farther from SkyTrain tracks to test if this has an effect on track alarm triggers.
4.3 Limitations
Regarding limitations of this research, they can broadly be attributed to time and approval constraints of large corporations such as TransLink, and practical concerns in experimental set- up. 64
Initial approval to expand the study sites to eight TransLink SkyTrain stations took approximately nine months, from January 2019 to September 2019. It was imperative to ensure that data would be collected for a full year so that results could be compared to claims made by
Innolytics of a 53% reduction in pigeon populations after one year of treatment (MacDonald &
Wolf, 2009), as well as previous studies that had conducted treatments periods for at least one year (Senar et al., 2021; Albonetti et al., 2015). This delay resulted in strained timelines as the initial intended project timeline was two years (January 2019 – December 2020), and resulted in
Lafarge Lake station not having a full year of data and ultimately removed from analysis.
Ideally, data collection for this type of project would start as early as possible so that technical concerns that arise can be addressed and all experimental sites are able to obtain at least one year of data.
Further, as excrement maintenance and abundance due to the pigeon populations were concerns at TransLink SkyTrain stations, data regarding customer complaints about excrement or the pigeons themselves was requested, as well as maintenance hours dedicated to cleaning pigeon excrement or work orders created to mitigate problems with the pigeons at various stations. However, due to security protocols and unavailability of data, this information was not obtained. It is recommended that data related to direct concerns expressed by those interested in the use of OvoControl® P be collected, as it allows for comprehensive assessment in determining the efficacy of OvoControl® P at directly mitigating concerns associated with pigeons.
There were numerous practical limitations with this research, notably theft and damage, the attraction of non-target pest species, and human error. As SkyTrain stations are located in central areas with high volumes of people traffic, theft is likely to occur if equipment is visible or 65
accessible to the general public. Multiple stations experienced theft and required purchasing replacement equipment: Braid station needed to be removed from the study entirely as no safe alternative location for the replacement feeder was available; VCC-Clark data collection ended prior to the intended date of March 15, 2021; Stadium-Chinatown theft was mitigated by moving the feeder into a fenced area adjacent to the original location; and Surrey Central was mitigated by placing the camera on the ground where it was not visible to those passing by. The occurrence of theft compounded study costs by requiring the purchase of replacement equipment and typically resulted in a loss of pigeon population count data for intervals of one to four weeks.
Further, the attraction of rats was another practical limitation of this study. Typically, feeders that were placed on the ground rather than roof tops would attract rats in varying population numbers. VCC-Clark station initially experienced up to 10 rats feeding in the areas, which was remedied by applying a mesh cover to the ground in areas they seemed to originate from.
Lafarge Lake station was selected as a replacement for Lougheed station as it experienced significant growth in the rat population to approximately 30. This population of rats was unacceptable to TransLink for maintenance reasons, as well as effecting the ability of pigeons to consume the cracked corn bait, as it would be eaten by rats shortly after being dispensed. It is important to consider the placement of feeders and the effect the potential location may have on attracting non-target species. Placing feeders on rooftops seemed most effective at mitigating this limitation, but due to the layouts of SkyTrain stations being different at each location, this was not always possible.
Lastly, human error is a limitation of this study as there are multiple instances where it can occur. As different technicians maintain the study sites through Terminix, occurrences where SD cards were placed in cameras incorrectly or batteries were not replaced happened on three 66
occasions, which led to a loss of pigeon population count data. Further, as different technicians investigate track alarm triggers and report varying degrees of detail and are responsible with classifying the cause of track alarm triggers as being either “Animal” or “Unknown,” it is possible that track alarm trigger events may not be reported in a consistent manner. Although efforts were made to mitigate error through the provision of a standard operating procedure for
Terminix technicians, as more people are involved in project maintenance, human error is unavoidable.
4.4 Recommendations and Application of Findings
Applications of the research findings could be relevant to a variety of settings in which the need for pigeon population control has been identified. These could include home or business clients of pest control companies such as Terminix, individual building sites, municipalities, or any site that has a consistent and relatively segregated population of resident pigeons.
However, when determining whether the use of OvoControl® P is appropriate, it is recommended to reference the principles for ethical wildlife control (Dubois et al., 2017) to formulate a management plan. The first principle states to modify human practices whenever possible (Dubois et al., 2017) and would be relevant to ensuring that humans are not intentionally or unintentionally feeding pigeon populations as this contributes to their population growth and persistence (Spenneman & Watson, 2017). If this is addressed sufficiently, further control measures may not be necessary. The second principle states to justify the need for control
(Dubois et al., 2017) and to ensure population management would contribute to mitigating current problems or issues directly related to pigeon populations. In this case, TransLink needs to keep its customers safe from track stoppages and risks associated with feces. The third principle 67
requires having clear and achievable outcome-based objectives (Dubois et al., 2017), which would be relevant to identifying a direct goal, for example in the case of TransLink, determining what number of pigeons would be an acceptable population, a percent decrease in track alarm triggers, or reduced hours dedicated to excrement maintenance. These objectives should be site and client specific and monitored for progress.
The fourth principle states to cause the least harm to animals (Dubois et al., 2017) and can be satisfied by using a non-lethal and non-invasive approach. The minimal-contact system of an automated feeder to dispense OvoControl® P and trail cameras to monitor populations without interference meets this principle. Further, it is important to minimize human interference with non-target species by placing feeders in locations that are not easily accessible to rats or other animals that may require removal. The fifth principle is to consider community values and scientific information (Dubois et al., 2017); thus, any interested user of OvoControl® P should consult current literature on recent findings and limitations of OvoControl® P use to modify practices accordingly. The use of OvoControl® P satisfies community values that identify with coexistence, as opposed to eradication, given the potential result is a small, but manageable, pigeon population.
The sixth principle is to include long-term systematic management (Dubois et al., 2017), and
OvoControl® P can meet these criteria as its efficacy relies on long-term management to ensure pigeons are ingesting OvoControl® P daily. This allows for modifications of the management program as needed and a comprehensive understanding of the population being managed. The seventh and final principle is to base control on specifics of the situation (Dubois et al., 2017), which is important as there isn’t one way to conduct or measure success of an OvoControl® P management program. Success must be defined for the specific site where management is 68
required, prior to starting an OvoControl® P management program, and methodology should be tailored to the physical location and layout of each specific site. Further, the label of pigeons as pests is not driving the control program, rather their impact on operations is.
A final consideration for potential applications of an OvoControl® P management program is cost. An initial start-up cost is approximately USD$364.99 per feeder and USD$219.99 per trail camera kit including batteries and SD cards. A 30lb bag of OvoControl® P costs USD$268.49 and cracked corn is USD$39.99 through Innolytics. It is recommended that one pound of
OvoControl® P be dispensed for every 80 birds daily (Innolytics, 2021). Therefore, long-term maintenance costs will vary depending on the size of the population. As OvoControl® P is regulated as a pesticide in Canada, if an interested user would like to maintain a management program, they need to obtain a Pest Control Applicators License (Structural) with the cost of the exam being CAD$90.00, with a minimum 75% score to pass, and additional costs for various optional supplementary study materials (British Columbia, 2021). Costs associated with hiring a pest control company to maintain an OvoControl® P management program may vary; the contract for Terminix to maintain TransLink SkyTrain stations was CAD$750 monthly for stations dispensing OvoControl® P and CAD$350 monthly for stations dispensing cracked corn, or CAD$4,200 monthly for all stations (Muxlox, 2021).
Overall, it is recommended that TransLink continue an OvoControl® P program to observe if population declines in treated stations occur over a longer a period of time and perhaps attempt moving feeders away from SkyTrain tracks to test if this has an impact on track alarm triggers. It is recommended that some measure of success be tracked, whether pigeon populations through the use of video monitoring, track alarm trigger data, excrement maintenance, or customer complaints regarding pigeons. It is recommended that Terminix expand their provision of 69
OvoControl® P services to interested customers using the ethical framework for wildlife control
(Dubois et al., 2017).
4.5 Future Research
There are many opportunities for future research that could contribute to understanding the efficacy and implications of an OvoControl® P management system in various settings. This could include conducting treatment studies for longer periods of time, conducting treatment in various settings, and more generally, studies that offer further understanding of free-ranging wildlife fertility control. A study to test how representative pigeons captured in a fixed camera position are of the overall population would be beneficial to understand how palatable treatment is to pigeons. A study spanning multiple years evaluating the efficacy of OvoControl® P at mitigating human-wildlife conflicts at TransLink SkyTrain stations would be beneficial to understand the long-term results and potential associated costs. Understanding this could help inform pigeon control management decisions by large corporations nationally facing similar human-wildlife conflicts. Further, a study performed in similar length to Albonetti and colleagues (2015), approximately eight years, would be beneficial in a municipal setting such as in research conducted by Senar and colleagues (2021), to observe if there are changes in population growth over a longer period of time. As OvoControl® P is intended to be used continuously as a long-term management solution, it is imperative to understand the effects of the contraceptive long-term.
Further, testing the efficacy of OvoControl® P in a variety of settings would be beneficial to understand under what conditions it can be used as a successful management solution. As Senar and colleagues (2021) stated that it was ineffective in a municipal setting, it would be beneficial 70
to understand under what conditions treatment can work, if it can be effective in some cities with particular geographic features, but not others. Further, it would be beneficial to know if
OvoControl® P could provide mitigation to human-wildlife conflicts in small-scale settings such as residential homes, single buildings, or parks.
Lastly, studies regarding the efficacy of free-ranging fertility control are scarce and lack longevity. Studies evaluating the use of contraceptives in free-ranging wildlife over the span of multiple years would be beneficial to inform human-wildlife conflict policy and support perspectives of co-existence and humane wildlife control.
4.6 Conclusion
In conclusion, pigeons are able to thrive in urban environments and human-wildlife conflicts may result in the form of excrement and disease risk. Numerous methods to control pigeon populations are currently available, the majority consisting of exclusion methods that have varying degrees of efficacy and lethal methods that do not provide lasting results. OvoControl®
P was tested at eight TransLink SkyTrain stations across the Lower Mainland of British
Columbia, Canada and it was ultimately found there was no change in pigeon populations at stations dispensing OvoControl® P and an increase in pigeon populations at stations dispensing cracked corn. It is recommended that TransLink continue to run an OvoControl® P population management program to assess if a population decline can be observed over longer periods of time and to assess whether OvoControl® P is an effective tool for human-wildlife conflict mitigation at TransLink SkyTrain stations.
71
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