Introduction
Crows are social birds that have been roosting communally in winter as far back as there are written accounts of crow behavior. Historically, crows have roosted in rural areas, but as cities developed they have moved into cities and started to roost here as there are larger amounts of waste food. It is unknown if cities grew into the crows roost areas of if the crows moved into cities but they can be found worldwide in a multitude of locations
Crow Life History
Who's Who
Two species of crow roam the plains of Kansas, both of them going and making roosts in populated cities on the eastern side of the state. These two are the American crow (Corcvus Brachyhnchos) and the Fish crow (Corvus ossifragus). The American crow is far more common and is the primary roosting crow in the state of Kansas.
When distinguishing between the two the American crow is almost twice the size as the fish crow and the fish crow has a more upright stance than the American crow. To the untrained eye you cannot tell the difference between them unless you see them side by side and see the size difference between the two. The the more trained birder the American crow makes your typical sound of “caw-caw” and the fish crow makes a sound termed as “uh-uh”, noted as sounding like they have an “attitude”.
American cows are more generalized birds and spend a majority of there time living in a large range of habitats, from farm fields and forests to large and small cities. On the other hand the Fish crow given its name can be found more frequently close to water systems, which in Manhattan we frequently see both as the farm fields surround us along with the large expanses of water sources surrounding the Manhattan area. The following with refer to both species just as “crows” as to simplify the process.
Annual Cycle
Knowing the annual process and behavior of crows is important to understand when looking at the processes of removing crows. We start with the breeding season of the crows, they begin breeding in the early to middle spring and nests can be found frequently with chicks in them through the summer, they have also been observed taking over vacant nests from other bird to simplify the process of building nests for their eggs. Crow only breed once per year and will renest if their nest is destroyed. In the winter northern crows migrate south staying together in their roosts, Kansas being one of the southern most states that the crows still migrate south, while others do stay in Kansas as some of the crows do not migrate and stay together in their roost throughout the year.
Food Habits
Crows are omnivorous, feeding on a large variety of agricultural products to a extremely large variety of peoples trash in the cities they reside in, also throwing in road kill and animals found in the dirt such as worms and reptiles. Given their wide range of food they are quite successful in sustaining populations. Most of their food coming from agricultural products such as grasses and plants substances, meanwhile trash being their lowest form of diet.
Behavior and social life
During the non breeding season crows are very social birds and for large community roosts that range in size of hundreds of birds to tens of thousands of birds. Crows are knows as one of the smartest and most intelligent birds in existence and a little known fact is that they have been noted to remember the face of people and can recognize a certain person. There are also resident and migrant birds as already talked about lightly. So with Kansas being in the middle of the country we not only see some of our birds migrate south we also see northern birds that migrate here and stay here for the remainder of their winter and then fly north when spring rolls around for breeding season.
Nuisance Problems
Like stated above crows can number in as few as 100 in a roost but can also range up to tens of thousands of birds, some estimated as nearly 50,000 birds large. When they congregate is when the problems start to arise. Depending on the location of the roost issues arise such as bird droppings all over city areas, which will shorten the life of buildings and structures through the chemicals in the droppings. They also present issues with sounds as they are loud during the day as well as night. They also have been noted to cause structure damage when the roost grows so large as well as the problems with them around airports causing issues with planes taking off and landing
Developing a Management Plan
The goal of presenting a crow management plan is to move crow somewhere where they can not impact the area with their excessive noise, damage problems, and dropping issues. It is important to have a good process in order to keep the birds from moving between multiple locations and causing problems in more locations than just one. However it is highly unlikely of being able to remove crows from a urban area completely.
Establish a Working Group
A key here is to try to work with the public, steak holders, and other communities that have been successful in ridding their cities of crows. The process will be far more successful if everyone is on board and working together instead of on their own.
Review Management Options
The first step is to find out options and what the extent of the problem is cause that can decide what needs to be done in order to best achieve results, as well It is also important for everyone to be aware of the limitations of any type of management. In almost all cases, you will be moving crows from one location to another, and this will need to be done on a regular basis each year. As you review your management options, also consider the likelihood of public acceptance of each option. In general, the larger the problem is perceived to be, the more tolerant the public will be of more extreme measures.
Establish Tolerance Zones
As a first step, decide which areas are particularly problematic for having roosting crows. These may be heavily trafficked areas, areas where people or cars congregate, parking lots, and areas like schoolyards where children gather. These areas can be established as "no-tolerance" zones, and crows will not be allowed to roost here. Your success will be greatest if you limit these areas to very specific locations as opposed to designating extensive areas of your urban site as no-tolerance zones.
Decide on Management Methods
As a group, you will need to decide what management methods you will use. These can range from no action at all to more extreme methods. A brief description of some options follows:
¥ No action–No coordinated plan of action. Individuals or groups may continue to attempt to move crows from local spots.
¥ Habitat management–Habitat management involves making the roosting area less attractive to crows. In many but not all cities, crows roost in large trees within urban areas. In some cases, habitat management has focused on thinning or removing the trees. This has worked fairly successfully for dispersing roosts of starlings and blackbirds. There is no indication that this is a successful strategy for moving crow roosts. In addition, large trees within the urban environment provide numerous benefits, so this strategy is generally not recommended. Crow roosts are often found in well-lighted areas, but nothing related to light manipulation has been found to work
¥ Harassment–Most crow roost relocation efforts involve harassment and moving crows from one location to another. The purpose is to disturb the roost and get them to move on to another location
¥ Training is necessary prior to the use of pyrotechnics as a harassment tool.
¥ Consider Your Workforce
¥ In addition to establishing a working group, you need to designate individuals who will be actively involved in the crow management process. A good option for a city like Manhattan is getting students from the college who are passionate about animals and the management of them such as the Park Management department.
Determine Your Budget
Budgets can range from volunteer only to the city taking control and ranging in mid thousands to tens of thousands of dollars depending on the process used to control the crow population.
Keep the Public Informed
It is essential that you let the public know what you are doing, why you are doing it, and where you are doing it. Talking to a local news outlet is a must so that you can reach more people than just doing a post on the city website. Keep the media informed as the process continues to keep the locals updated on the issues as hand with the crow management. Finally, it is important to keep those that are working on the management and keep them in a obvious attire so those in the public know what is happening and who is working on the management of it.
Monitor the Roost Location
Once the crows have relocated it is important to track the location of the roost of crows in order to see where they are going and if they start relocating back to your area.
Begin Roost Management Early in the Season
The earlier you start the easier it will be to control as if you can elimitate the nesting areas then the crows will tend to move on to other locations to nest in an area that isn’t harmful to them.
Legal Status of crow management
Crows are legally protected by the federal Migratory Bird Treaty Act. In Kansas there is a open season provided by KDWPT and it is a all winter long hunting season. However there is nothing that states non lethal uses are not allowed with the protection of the crow.
Listed below are a variety of management techniques. Management will be most successful if you use an integrated approach that incorporates the use of multiple management tools. Reliance on a single practice is often much less successful.
Harassment
PYROTECHNICS
The most common form of harassment involves shooting off bangers, shell crackers, bird whistlers, and screamers that produce a loud sound similar to firecrackers. These are useful for moving birds away from a particular location.Shooting pyrotechnics is frequently used to disperse roosts in most cities.
DISTRESS CALLS
Alarm and distress calls are used to communicate danger or warning. Broadcast of species-specific distress calls have been used as an additional deterrent at roosts. These generally work best in combination with other techniques. As with other techniques, birds may habituate to them so their value is usually of short duration. However, used sparingly and with other techniques they can improve the effectiveness of a roost relocation program.
LOW-POWERED LASERS
Low-powered lasers, which give off a beam of red light, have been shown to be effective in moving crows away from a roost location. However, the birds tend to move back to the same roost site unless lasers are used along with other techniques such as pyrotechnics and distress calls. Low-powered lasers do not cause damage to the eye, but they do elicit an avoidance response in crows. A downside of lasers is that they are expensive: a single unit costs around $1,200. However, some companies will lease lasers for use on a weekly basis.
METHYL-ANTHRANALITE
Methyl-anthranalite is the active ingredient in a fogging agent that has been occasionally used on roosting birds. It does not depend on birds eating it, but instead the birds are exposed to the fog when roosting. The fog acts as an irritant, making the birds uncomfortable. Because it is a contact repellent and only works when birds are exposed to it, repeating applications will likely be needed to maintain effectiveness in order to keep the birds at bay
Effigies
Effigies are artificial crow models sold commercially for decorative purposes such as Halloween displays. The purpose of using an effigy for roost management is to make the crows returning to the roost see the "dead crow" and conclude that this site is obviously not a good place to roost. Effigies are most successful when used sparingly and in conjunction with other techniques to reinforce the message that there are hazards associated with a particular roost site.
Effigies should be hung upside down from a tree branch near the top of a centrally located tree.
Lethal Methods
While nonlethal dispersal methods may be effective, crows may become habituated to them, because of their intelligence and tenacity. Targeted shooting of crows may help to reinforce the message that a particular location is a bad place to roost. However, it often is not a viable option in urban areas where most problems with roosting crows occur. The toxicant DRC-1339 is a restricted-use pesticide that has been approved for use by USDA Wildlife Services personnel in selected states on a case-by-case basis. Toxicants generally do not provide long-term solutions for large urban roosts, and public opposition may not support this option.