Texas is a major route for migratory birds
and serves as a breeding site
for egrets and herons.
During nesting season, most egrets
and herons gather in large colonies,
known as rookeries, to nest.
These rookeries include species
such as cattle egrets,
little blue herons,
snowy egrets,
great egrets,
and yellow crown night herons.
In Texas, cattle egrets are typically
the most abundant species.
Different species arrive, nest, and leave
at various times throughout the nesting season,
which typically lasts from mid-February
to late October.
Adult birds and their offspring
often return to the same location
every year.
Over time rookeries can increase in size.
Nesting egrets and herons prefer areas
with mature trees and at least 75 percent
closed canopy with overlapping branches.
This allows the birds to easily walk
among the branches from tree to tree.
Most rookeries
are located near water
where there is plenty of food
available for them to eat,
but rookeries
can easily exist away from water
in urban areas.
When egrets and herons establish rookeries
in an urban setting,
it can become a nuisance.
The noise, odor,
regurgitated food, large amounts of feces,
and even deceased birds at the rookery site
can be a challenge.
When located adjacent to airports
rookeries can potentially interfere with aircraft.
Egrets and herons are protected
by state and federal laws.
It is illegal to kill, harass, or
disturb the birds in any way
that could cause nest abandonment
or the death of eggs or hatchlings.
Once the first bird lays an egg,
all harassment and scare techniques
must stop.
Up to that point it is legal
to harass or scare the birds
to deter them from an undesired location.
Once a rookery is established,
complete removal is not possible,
however you can prevent a rookery
from establishing or returning the next year.
Habitat modification is most effective
and produces the longest lasting prevention
of rookery establishment.
In the winter months,
when the birds are gone
modify habitat by creating
openings within the canopy
and removing overlapping branches
making the area less desirable
for the birds.
Dramatic changes are not necessary.
Remove dead wood and thin the tree canopy
to allow sunlight between limbs and other trees.
Also remove excessive undergrowth vegetation
and old abandoned nests.
At the beginning of nesting season,
remove early nesting material daily
using long poles or water hoses
after verifying that no eggs are present.
For maximum impact, habitat modifications
should be combined with noise
and visual deterrents.
When birds first arrive in early spring,
they are somewhat nervous
and easily scared away.
Noise deterrents such as pyrotechnics,
cracker shells, propane cannons,
and predator calls, work effectively.
Local residents can be encouraged
to use noisemakers, air horns, clackers,
and even pots and pans to deter the birds
from undesired nesting sites.
Visual deterrents,
such as scare eye balloons, mylar streamers,
and hawker owl silhouettes
can be effective when put in the trees
of potential nesting sites.
To be most effective, combine several
of these methods so that the birds
do not become accustomed to them.
Public awareness and early detection
are critical to prevent nuisance rookeries.
The more residents participating
in early detection and deterrent techniques,
the better the chance
of getting the birds to go elsewhere.
It is important to remember
that once the first bird lays an egg,
all harassment and scare techniques
must stop.
It is illegal to kill, harass, move,
or disturb the birds or nests
when they are actively nesting.
If a rookery is established in an urban area
and the birds are nesting, residents may continue
normal maintenance of their property,
such as mowing, weed eating,
edging, and watering.
To keep feces from accumulating,
power washers spray down sidewalks,
lawns, landscaping, and buildings
on a regular basis.
Residents should be advised
not to handle the birds,
or specifically disturb the birds while nesting.
Fallen eggs, injured, or dead birds
should be reported to the local municipality.
When trying to prevent
a rookery from developing,
it is possible that the birds will move
to another location that is just as undesirable.
Municipalities should develop
a contingency plan
in anticipation of actions to be taken
should the need arise.
The Texas Parks and Wildlife
Urban Program provides assistance
to municipalities dealing with urban rookeries.