**3. How to relieve the pigeon problem?**

#### **3.1 Removal of pigeons**

One tactic to rid pigeons of an area is by humanely capturing them and transferring them to a new location [7]. This strategy has been proven to be ineffective, due to biological characteristics of pigeons. Pigeons have an excellent homing ability. Immediately after fledging, pigeons become imprinted to the site [36]. When taken to an unknown location, a pigeon will orient itself by using the Sun's orientation [37], Earth's geomagnetism [38], environmental odors [39], and landmarks [40] to navigate themselves homeward.

#### **3.2 Killing pigeons**

Another tactic to rid pigeons of an area is through euthanasia or culling. However, the tactic often is ineffective at decreasing pigeon abundance [18]. In Basel, Switzerland in the 1980s, pigeon populations were reduced by 80% through euthanasia. Within a few weeks, pigeon populations returned to the original size or even larger than before [41]. The removal of individuals opened up space for new migrants to come in, such as juveniles [41]. Because in urban areas pigeons reproduce throughout the year and have reduced mortality rates due to reduced predation, flock sizes can exceed carrying capacities and competition for breeding sites can increase [42].

In Stuttgart, Arkansas, controlled hunting was used to decrease pigeon abundance. Following the hunt, pigeon numbers decreased dramatically but within a few months rose to original levels [43]. From 1983 to 1991, Barcelona, Spain started a program of capturing and euthanizing pigeons. One single capture caught 362 individuals. However, pre- and post-census showed no significant difference in abundance [44]. Killing pigeons has proven to be only a temporary solution. Due to their high fertility rates, pigeons can rebound quickly.

**43**

**Figure 2.**

*University in 2017.*

out the year [47].

*Ecology of Feral Pigeons: Population Monitoring, Resource Selection, and Management Practices*

A management plan can become successful by carefully studying what an organism selects for within its habitat. Pigeons are granivorous [7] and need a large feeding source to support their large population and offspring [7]. Furthermore, if

When killing pigeons proved ineffective for the city of Basel, the local government tried to decrease abundance by decreasing pigeon food supply [41]. In their situation, people created a huge food base for pigeons. They instituted an outreach program to educate people on the harm of feeding pigeons and the importance of maintaining a small population [41]. The decrease in food supply increased competition, decreased the probability of juveniles entering the population, and decreased reproductive success due to unfavorable conditions [41]. Within 4 years, one of the

However, finding the primary source of food for pigeons may be difficult. Pigeons are opportunistic species [7] and have the ability to exploit a variety of food types [12], even human refuge [7]. Therefore, pigeons will feed within cities, consuming food left behind by humans, and can also travel to the outskirts of urban areas to eat from agricultural fields [7]. While it is common to see pigeons eating food distributed by humans, this rarely represents a high percentage of their diet [7]. Instead, pigeons are more likely to select grain from agricultural sources or from wild plants [7]. Therefore, simply limiting the food source may only have a limited effect. Moreover, such an effect depends on the foraging behavior of the flock [7]. If the majority of a flock feeds on a source that can potentially be man-

If an organization has a population that forages outside their property, similar to the situation at TTU, influencing nest sites may be a more favorable way to decrease abundance than limiting the food source. As we have mentioned in this chapter, pigeons are prolific breeders. For most avian species, the breeding period is seasonal [46]. Pigeons have the advantage of being granivorous, where their food supply can survive during the winter months [7]. This consistent food supply helps pigeons feed their offspring with crop milk throughout the year [7]. Interestingly, wild rock pigeons have a seasonal breeding period, while feral pigeons breed throughout the year, even in winter (**Figure 2**) [46]. The ability to do so is probably due to the selective breeding done by humans in the past to produce a bird that can breed through-

The typical clutch size of feral pigeons is two eggs, very rarely is it more or less [7]. The incubation period lasts approximately 2 weeks, and depending on region and season, chicks will fledge from approximately 25–40 days after hatching [6, 7].

*Average number of eggs, chicks and juvenile pigeons on the experimental sciences building at Texas Tech* 

a pigeon does not eat in 3 days, it can lose up to 5% of its body weight [45].

central flock sizes went from 1400 to 708 pigeons [41].

aged, then it is possible to decrease their abundance [7].

*DOI: http://dx.doi.org/10.5772/intechopen.84612*

**3.3 Modifying habitat**

*Ecology of Feral Pigeons: Population Monitoring, Resource Selection, and Management Practices DOI: http://dx.doi.org/10.5772/intechopen.84612*

#### **3.3 Modifying habitat**

*Wildlife Population Monitoring*

Information on fluctuations in pigeon abundance can help when trying to organize a successful management plan. For example, we can determine if decreases in pigeon abundance are due to seasonal variation or due to management strategies, or when efforts to decrease abundance could be eased or made more active. However, to determine the most effective management for decreasing pigeon numbers,

*Seasonal counts in the morning and afternoon of pigeons on two buildings on Texas Tech campus in 2017.* 

One tactic to rid pigeons of an area is by humanely capturing them and transferring them to a new location [7]. This strategy has been proven to be ineffective, due to biological characteristics of pigeons. Pigeons have an excellent homing ability. Immediately after fledging, pigeons become imprinted to the site [36]. When taken to an unknown location, a pigeon will orient itself by using the Sun's orientation [37], Earth's geomagnetism [38], environmental odors [39], and landmarks [40] to

Another tactic to rid pigeons of an area is through euthanasia or culling. However, the tactic often is ineffective at decreasing pigeon abundance [18]. In Basel, Switzerland in the 1980s, pigeon populations were reduced by 80% through euthanasia. Within a few weeks, pigeon populations returned to the original size or even larger than before [41]. The removal of individuals opened up space for new migrants to come in, such as juveniles [41]. Because in urban areas pigeons reproduce throughout the year and have reduced mortality rates due to reduced predation, flock sizes can exceed carrying capacities and competition for breeding

In Stuttgart, Arkansas, controlled hunting was used to decrease pigeon abundance. Following the hunt, pigeon numbers decreased dramatically but within a few months rose to original levels [43]. From 1983 to 1991, Barcelona, Spain started a program of capturing and euthanizing pigeons. One single capture caught 362 individuals. However, pre- and post-census showed no significant difference in abundance [44]. Killing pigeons has proven to be only a temporary solution. Due to

their high fertility rates, pigeons can rebound quickly.

further understanding of ecology is necessary.

*ESB = experimental science building, HH = holden hall. Standard error ± 1.*

**3. How to relieve the pigeon problem?**

**3.1 Removal of pigeons**

**Figure 1.**

navigate themselves homeward.

**3.2 Killing pigeons**

sites can increase [42].

**42**

A management plan can become successful by carefully studying what an organism selects for within its habitat. Pigeons are granivorous [7] and need a large feeding source to support their large population and offspring [7]. Furthermore, if a pigeon does not eat in 3 days, it can lose up to 5% of its body weight [45].

When killing pigeons proved ineffective for the city of Basel, the local government tried to decrease abundance by decreasing pigeon food supply [41]. In their situation, people created a huge food base for pigeons. They instituted an outreach program to educate people on the harm of feeding pigeons and the importance of maintaining a small population [41]. The decrease in food supply increased competition, decreased the probability of juveniles entering the population, and decreased reproductive success due to unfavorable conditions [41]. Within 4 years, one of the central flock sizes went from 1400 to 708 pigeons [41].

However, finding the primary source of food for pigeons may be difficult. Pigeons are opportunistic species [7] and have the ability to exploit a variety of food types [12], even human refuge [7]. Therefore, pigeons will feed within cities, consuming food left behind by humans, and can also travel to the outskirts of urban areas to eat from agricultural fields [7]. While it is common to see pigeons eating food distributed by humans, this rarely represents a high percentage of their diet [7]. Instead, pigeons are more likely to select grain from agricultural sources or from wild plants [7]. Therefore, simply limiting the food source may only have a limited effect. Moreover, such an effect depends on the foraging behavior of the flock [7]. If the majority of a flock feeds on a source that can potentially be managed, then it is possible to decrease their abundance [7].

If an organization has a population that forages outside their property, similar to the situation at TTU, influencing nest sites may be a more favorable way to decrease abundance than limiting the food source. As we have mentioned in this chapter, pigeons are prolific breeders. For most avian species, the breeding period is seasonal [46]. Pigeons have the advantage of being granivorous, where their food supply can survive during the winter months [7]. This consistent food supply helps pigeons feed their offspring with crop milk throughout the year [7]. Interestingly, wild rock pigeons have a seasonal breeding period, while feral pigeons breed throughout the year, even in winter (**Figure 2**) [46]. The ability to do so is probably due to the selective breeding done by humans in the past to produce a bird that can breed throughout the year [47].

The typical clutch size of feral pigeons is two eggs, very rarely is it more or less [7]. The incubation period lasts approximately 2 weeks, and depending on region and season, chicks will fledge from approximately 25–40 days after hatching [6, 7].

#### **Figure 2.**

*Average number of eggs, chicks and juvenile pigeons on the experimental sciences building at Texas Tech University in 2017.*

In Manchester, eggs hatched were approximately 62%, and chicks that fledged were around 66% [6]. Once chicks reached about 20 days of age, pigeons started laying another clutch [6]. With high reproductive success and year-long output, pigeon abundance can quickly increase.

Managing pigeon habitat via nest site removal could decrease reproductive output and decrease abundance. First, it is advantageous to locate areas that are selected for in terms of nesting locations. Pigeons typically nest in cavity-like structures on top of or within buildings (**Figure 3**) [7]. Any site that is covered and semi-dark provides a favorable site for pigeons to nest [7]. Nests can be found from inside attics to the underside of bridges and overpasses [7]. On TTU campus, pigeon nests can be found under heating, ventilation, and air conditioning (HVAC) equipment on top of buildings (**Figure 3**) that are protected from the elements and can provide a stable environment (e.g. temperature).

Modifying nest sites, such as blocking them off with screens or completely removing areas that house colonial nest sites, can reduce pigeon abundance [7]. Another strategy is removing or destroying eggs periodically. Dovecotes, structures used to house pigeon nests, have been used in cities to reduce egg production. However, maintenance of dovecotes can be time-consuming and costly, and removal of eggs may trigger pigeons to lay more [48]. Also, the use of dovecotes has not proven to be effective [18].

## **3.4 Chemical sterilization**

Chemical sterilization is a humane strategy to decrease abundance but does not get rid of the entire population [7]. Research conducted on the effect of decreasing reproductive output through sterilization did decrease abundance in feral pigeons (among other species) and was more effective than killing individuals [49]. However, the majority of studies have been conducted in laboratory settings. How effective sterilization is in field settings with natural populations is not well understood.

#### *3.4.1 Nicarbazin*

Texas Tech University is investigating how OvoControl (Innolytics, LCC) can limit reproductive success and decrease abundance. The active ingredient in OvoControl is Environmental Protection Agency approved nicarbazin in the form of a ready-to-use bait. First developed to decrease the growth of coccidian parasites in chickens, researchers found that nicarbazin decreased egg production and

**45**

*Ecology of Feral Pigeons: Population Monitoring, Resource Selection, and Management Practices*

hatchability by compromising the internal egg structure and sperm receptors [50]. When consumed by a female, the hatchability rates decreased to near zero with no

In Rimini, Italy, a population management strategy was conducted to decrease pigeon abundance with Ovistop (a similar bait with nicarbazin as the active ingredient) [51]. Using 10 locations and dispensing bait from March to November in 2005 and 2006, there was a decrease in abundance by 48% [51]. The city of Modena, Italy sought to decrease pigeon abundance but wanted to make sure that native swifts and bats could still flourish. They dispensed Ovistop and decreased the number of nesting locations [52]. The scaffold holes around the city that pigeons used for nesting were not completely covered, but reduced in size to allow bats and swifts to roost inside [52]. This program led to a decrease in pigeon abundance from 1060

Innolytics, LCC helped the city of San Diego study how OvoControl influenced natural pigeon populations. Two sites that housed approximately 150 individual pigeons each were selected for the study. At the first site, they dispensed OvoControl for the pigeons to consume. At the second site, they did not dispense OvoControl to see how the population progressed without the influence of sterilization techniques. Within the first year of dispensing the bait, there was a decrease in pigeon abundance by 53% [53]. After 28 months, the population decreased by 88% [53].

Texas Tech University has been working closely with Innolytics, LCC to make sure that OvoControl is used as effectively as possible. We have found it to work best on top of flat buildings, where there are hot spots in abundance. To attract pigeons to the location, we dispensed cracked corn with deer feeders. Once an adequate number of pigeons were coming to the area to consume the corn, we slowly integrated OvoControl into the deer feeders. We started this process on top of the Biology building and HH in May of 2018. We are examining how effective the treatment is by candling eggs to look at fertilization rates [54] and abundance

Avian birth control decreases abundance by decreasing the number of pigeons entering the population through birth [54]. Due to pigeons being social and territorial, the feeders should only attract local flocks. Once the population decreases, no new pigeons should enter the area due to individuals from the current flock still being present and defending their roosting/nesting location [55]. However, once pigeons stop eating OvoControl, it can lose its effect within 1 week [55]. By placing feeders on top of buildings, exposure to native birds is limited. There are also no secondary trophic effects. Hawks will not be affected after preying on a pigeon that has consumed

Another way to decrease habitat favorability for pigeons is to decrease roosting availability. Buildings are full of ledges for pigeons to roost on, and there are many ways to decrease roost selection. Increasing the angle of the ledge to 45° or more by using sheet metal or other materials can discourage pigeons from roosting or nesting on ledges [56]. Netting or mesh can be used as well. Texas Tech University has decreased roosting and nesting by screening off balconies that housed a large colony of pigeons. Netting can be placed below rafters to discourage pigeons from

Porcupine wires are spikes that can also be placed on ledges to prevent pigeons

from roosting [56]. The stainless steel spikes point in all directions and cause discomfort for pigeons who try to roost in the location [57]. A bird shocking device

OvoControl [53]. OvoControl is only useful if it is directly consumed [55].

*DOI: http://dx.doi.org/10.5772/intechopen.84612*

pigeons to 205 pigeons in downtown Modena [52].

other side effects [50].

throughout the year.

**3.5 Limiting roosting locations**

roosting in barns and sheds [56].

#### **Figure 3.** *Pigeon nests under a HVAC machine on top of the Biology building on TTU campus.*

*Ecology of Feral Pigeons: Population Monitoring, Resource Selection, and Management Practices DOI: http://dx.doi.org/10.5772/intechopen.84612*

hatchability by compromising the internal egg structure and sperm receptors [50]. When consumed by a female, the hatchability rates decreased to near zero with no other side effects [50].

In Rimini, Italy, a population management strategy was conducted to decrease pigeon abundance with Ovistop (a similar bait with nicarbazin as the active ingredient) [51]. Using 10 locations and dispensing bait from March to November in 2005 and 2006, there was a decrease in abundance by 48% [51]. The city of Modena, Italy sought to decrease pigeon abundance but wanted to make sure that native swifts and bats could still flourish. They dispensed Ovistop and decreased the number of nesting locations [52]. The scaffold holes around the city that pigeons used for nesting were not completely covered, but reduced in size to allow bats and swifts to roost inside [52]. This program led to a decrease in pigeon abundance from 1060 pigeons to 205 pigeons in downtown Modena [52].

Innolytics, LCC helped the city of San Diego study how OvoControl influenced natural pigeon populations. Two sites that housed approximately 150 individual pigeons each were selected for the study. At the first site, they dispensed OvoControl for the pigeons to consume. At the second site, they did not dispense OvoControl to see how the population progressed without the influence of sterilization techniques. Within the first year of dispensing the bait, there was a decrease in pigeon abundance by 53% [53]. After 28 months, the population decreased by 88% [53].

Texas Tech University has been working closely with Innolytics, LCC to make sure that OvoControl is used as effectively as possible. We have found it to work best on top of flat buildings, where there are hot spots in abundance. To attract pigeons to the location, we dispensed cracked corn with deer feeders. Once an adequate number of pigeons were coming to the area to consume the corn, we slowly integrated OvoControl into the deer feeders. We started this process on top of the Biology building and HH in May of 2018. We are examining how effective the treatment is by candling eggs to look at fertilization rates [54] and abundance throughout the year.

Avian birth control decreases abundance by decreasing the number of pigeons entering the population through birth [54]. Due to pigeons being social and territorial, the feeders should only attract local flocks. Once the population decreases, no new pigeons should enter the area due to individuals from the current flock still being present and defending their roosting/nesting location [55]. However, once pigeons stop eating OvoControl, it can lose its effect within 1 week [55]. By placing feeders on top of buildings, exposure to native birds is limited. There are also no secondary trophic effects. Hawks will not be affected after preying on a pigeon that has consumed OvoControl [53]. OvoControl is only useful if it is directly consumed [55].

#### **3.5 Limiting roosting locations**

Another way to decrease habitat favorability for pigeons is to decrease roosting availability. Buildings are full of ledges for pigeons to roost on, and there are many ways to decrease roost selection. Increasing the angle of the ledge to 45° or more by using sheet metal or other materials can discourage pigeons from roosting or nesting on ledges [56]. Netting or mesh can be used as well. Texas Tech University has decreased roosting and nesting by screening off balconies that housed a large colony of pigeons. Netting can be placed below rafters to discourage pigeons from roosting in barns and sheds [56].

Porcupine wires are spikes that can also be placed on ledges to prevent pigeons from roosting [56]. The stainless steel spikes point in all directions and cause discomfort for pigeons who try to roost in the location [57]. A bird shocking device

*Wildlife Population Monitoring*

abundance can quickly increase.

not proven to be effective [18].

**3.4 Chemical sterilization**

understood.

*3.4.1 Nicarbazin*

can provide a stable environment (e.g. temperature).

In Manchester, eggs hatched were approximately 62%, and chicks that fledged were around 66% [6]. Once chicks reached about 20 days of age, pigeons started laying another clutch [6]. With high reproductive success and year-long output, pigeon

Managing pigeon habitat via nest site removal could decrease reproductive output and decrease abundance. First, it is advantageous to locate areas that are selected for in terms of nesting locations. Pigeons typically nest in cavity-like structures on top of or within buildings (**Figure 3**) [7]. Any site that is covered and semi-dark provides a favorable site for pigeons to nest [7]. Nests can be found from inside attics to the underside of bridges and overpasses [7]. On TTU campus, pigeon nests can be found under heating, ventilation, and air conditioning (HVAC) equipment on top of buildings (**Figure 3**) that are protected from the elements and

Modifying nest sites, such as blocking them off with screens or completely removing areas that house colonial nest sites, can reduce pigeon abundance [7]. Another strategy is removing or destroying eggs periodically. Dovecotes, structures used to house pigeon nests, have been used in cities to reduce egg production. However, maintenance of dovecotes can be time-consuming and costly, and

removal of eggs may trigger pigeons to lay more [48]. Also, the use of dovecotes has

Chemical sterilization is a humane strategy to decrease abundance but does not get rid of the entire population [7]. Research conducted on the effect of decreasing reproductive output through sterilization did decrease abundance in feral pigeons (among other species) and was more effective than killing individuals [49]. However, the majority of studies have been conducted in laboratory settings. How effective sterilization is in field settings with natural populations is not well

Texas Tech University is investigating how OvoControl (Innolytics, LCC) can limit reproductive success and decrease abundance. The active ingredient in OvoControl is Environmental Protection Agency approved nicarbazin in the form of a ready-to-use bait. First developed to decrease the growth of coccidian parasites in chickens, researchers found that nicarbazin decreased egg production and

*Pigeon nests under a HVAC machine on top of the Biology building on TTU campus.*

**44**

**Figure 3.**

(Bird-shock, Flex-Track) can also be placed almost anywhere and has limited visibility. The device shocks the bird enough to scare it away, without harming the bird [57].

Noise-making devices such as those that emit a high-frequency sound have proven to be ineffective in removing pigeons [56]. Scaring pigeons with lights, fake snakes, owls, and other devices also seem ineffective on pigeon abundance [56]. Chemical repellents have also been used to decrease pigeon presence [56]. While effective at first, pigeons can get used to the repellent and decrease repellent effectiveness [56].

#### **3.6 Birds of prey**

Falconry is becoming a popular and "new" method in pigeon management. Using falcons may be a useful technique if there is no way to pigeon proof an area or a building [58]. Birds of prey can scare away pigeons and greatly influence their behavior [58]. In Calgary, falcons have been released at the South Health Campus [59]. Effectiveness of commercial use falconry or having falcons permanently live on buildings is not known. Increase in predator abundance within a location would be more beneficial than in areas where pigeons have very few predator encounters. Such an approach may be more beneficial than using fake owls. Pigeons can become accustomed to fake owls and no longer fear them [56].
