Gull Rooftop Deterrents Design Guidelines butterfly

Why Deter Gulls from Rooftops?gull-1

The Western Gull spends most of its winters along the Central California coast. These migratory birds are commonplace along the coast, especially in urbanized locations. The abundance of gulls along coastal towns and cities can be a nuisance to the communities for various reasons. 

Gulls have adapted to foraging for food from dumpsters which are not properly secured, they are bold enough to grab food from people eating outdoors (restaurants, cafés, and beach or park picnics), as well as stealing food from open backpacks and bags when left unattended.

In addition to being a nuisance to the local community and tourists who visit Pacific Grove, gulls leave feces droppings on rooftops and sidewalks. When it rains or when the rooftop or sidewalk surfaces are washed with water, the feces from the rooftops and sidewalks flow with the stormwater runoff. This contaminated runoff leads directly to Monterey Bay adding to the water pollution problem. 
Western Gulls nest and lay eggs from March through May. Nests are made on rooftops, inside eaves, heating, ventilation, and cooling equipment (HVAC equipment), as well as other kinds of vents or ducts, especially in parts of the business district of Pacific Grove. This causes expensive infrastructure repairs and the possible need to replace of such equipment.gull-2  gull-3

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Planning Gull Rooftop Deterrent StrategiesGull rooftop deterrents are methods to deter birds from landing, roosting, and nesting. It is important to use bird control products that do not harm birds, other animals, or people. Western gulls and their eggs are protected under Federal Migratory Bird Treaty Act and the State Fish and Game Code 3503.

Benefits to deterring gulls include:

  • Keeps nesting birds out of expensive rooftop equipment areas and HVAC units
  • Keeps rooftop clean from contaminants entering the storm drain
  • Reduce the need for rooftop cleaning
  • Eliminate smells
  • Decrease bird noise

One effective method of deterring gulls is to remove their ability to land and nest on rooftops. 

Types of Physical DeterrentsBirds quickly adapt to most static bird control devices after exposure to false threats. The gull deterrent devices that are most effective physically block birds. Below is a list of some examples of physical deterrents devices.

Steel or Plastic Spike Systems
A row of needles or spikes pointing vertically upwards. The spikes are intended to make it difficult for larger birds to land and perch. This product is generally used on horizontal surfaces such as ledges or window sills, where birds are known to roost or nest.


  • Easy to install
  • Long life span
  • Environmentally safe
  • Effective against most species of birds


  • Limited to use of ledges
  • Tend to collect debris between the spikes (droppings, feathers, nesting material)
  • Cleaning is recommended
  • Ineffective against smaller birds
  • May not affect gull nesting opportunities 
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Netting Systems: This system is intended to eliminate the bird control problem by preventing birds from nesting in recessed portions of the building, light wells, or under eaves. The netting protects the buildings. Polyethylene or polypropylene are recommended to make the netting as both materials withstand tension without stretching. Netting to match building colors is available and if hung correctly, can be fairly inconspicuous.


  • Suitable for large areas
  • Can last up to 15 years
  • Environmentally safe
  • Effective against most species of birds


  • Ineffective if there are gaps or holes in the netting.
  • Accurate installation is difficult and can be expensive.
  • May obscure some architectural elements
  • Difficult access to roof systems
  • Gulls have been known to perch on draped netting 

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Anti-Roosting Wire Systems: Consists of a series of parallel wires supported by narrow pins held under tension by small sprints. The spacing of the wires is intended to prevent birds from gaining a strong foot hold on ledges. 


  • Causes minimal damage to building as the narrow stainless steel pins used for support are small enough to be drilled into the mortar joints. If and when the pins need to be removed, the holes made can be refilled.
  • Can last up to 10 years
  • Environmentally safe


  • Limited to use of ledges
  • Not effective with all species of birds (mostly an anti-pigeon method)
  • May not affect gull nesting opportunities

gull-10  gull-11InstallationInstall the gull deterrent device applicable to your rooftop situation. Follow the manufacturer’s recommendations for installation. Building owners may need to consult with a bird deterrent expert and hire a contractor for installation.

Rooftops are often connected within urban blocks. Consider a gull rooftop deterrent strategy that can be shared by all rooftops in the block. This coordination creates a more effective deterrent and may save overall costs for the product and its installation.

Cleaning Rooftops and SidewalksPacific Grove has a stormwater diversion system in place at certain times of year. During the time the diversion system is operable, cleaning/washing of rooftops and sidewalks is permissible. Contact the City of Pacific Grove Planning Division for more information before you clean or wash: 831-648-3190.

If you must wash rooftops or sidewalks when the diversion system is not operating, there are required measures that need to be taken so the wash runoff does not flow into the storm drains. This runoff is considered an illegal discharge which pollutes Monterey Bay. Contact the City of Pacific Grove Planning Division for more information before you clean or wash: 831-648-3190.

  • Follow recommended maintenance procedures applicable to the deterrent device installed.
  • Wash and Clean surfaces that are contaminated with bird droppings by following Local Municipal Code Requirements and Best Management Practices. Contact the City of Pacific Grove Planning Division for more information, including the best time to clean and wash: 831-648-3190.

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