Download The importance of Wood Duck management:How

The importance of Wood Duck management:
How can we best insure higher survival rate?
Heather Sunny
SCI 503B
SPRING 2012
1
INTRODUCTION
As more and more natural wetlands in the United States are drained and converted to
agricultural, industrial, and residential uses, remaining habitat has become increasingly important
for migratory water fowl. Specifically, wood duck populations reliant on the natural flow regime
have been devastated and current management efforts seek to mitigate the effects of habitat loss
by providing artificial nest boxes. Successful breeding and use of the nest boxes depends on a
myriad of factors including facing water, distance to water, height in tree, etc. I set out to
determine how we can best insure a high rate of habitation in the nest boxes erected within the
Cache River Wetlands in Southern Illinois.
Wetlands
Wetlands are found from the tundra to the tropics, and on every continent except Antarctica.
Wetlands and comprise important features that provide beneficial services for people and
wildlife; they protect water quality through filtration, provide valuable habitat, store water which
reduces flooding, and provide valuable habitat. These beneficial services are considered
valuable to us worldwide because they have unique and natural characteristics that you can’t find
anywhere else.
Water filtration. Wetlands are also a source of water filtration (EPA 2012). When water pools
up in a wetland, sediment in the overflow starts settle to the floor of the wetland. The nutrients
from fertilizer application, manure, leaking septic tanks, and municipal sewage that are carried as
runoff are absorbed by plant roots and microorganisms in the soil (EPA 2012). This filtration
process removes much of the water’s nutrient and pollutant load by the time it leaves the
wetland. Some types of wetlands are so good at their filtration function that environmental
managers construct similar artificial wetlands to treat storm water and wastewater.
2
Storage and flood control. Wetlands also store floodwaters and maintain surface water flow
during dry periods (EPA 2012). One of the main functions of wetlands is to store rising water
and then to slowly release this water. While it is storing the overflow of water it allows for
ground water to recharge and contribute to the base flow of surface water systems in the process
(EPA 2012). The wetlands also reduce flood heights by storing enormous amounts of water,
which reduces the risk of potential flood damage, saving money and property (EPA 2012).
Valuable habitat. More than one-third of the United States' threatened and endangered species
live only in wetland areas, and nearly half of those species use wetlands at some point in their
lives (EPA 2012). Many other animals and plants depend on wetlands for survival (EPA 2012).
Many of the U.S. breeding bird populations which includes ducks, geese, woodpeckers, hawks,
wading birds, and many song-birds feed, nest, and raise their young in wetland areas (EPA
2012). Migratory waterfowl use coastal and inland wetlands as resting, feeding, breeding, or
nesting grounds for at least part of the year.
Wetlands have an even greater importance because some species of migratory birds are
completely dependent on certain wetlands and would become extinct if those wetlands were
destroyed (EPA 2012). If new wetlands are constructed with duck production in mind, wood
ducks will use them for nesting, brood rearing and roosting along with a multitude of other
wildlife species. Unfortunately, we see that more natural wetlands are being drained to make
room for agricultural, industrial and residential uses (Bromley et al. 2009). Now the remaining
waterfowl production areas are even more valuable for water fowl production. In order to
maintain water fowl habitats we need to turn to creating new wetlands on private lands and
conservation on existing ones. This is key to sustaining wildlife resources
Wood Duck Habitat and Management
3
Wetlands provide the improved water quality and wildlife habitat important for wood duck
populations, which rely on wooded swamps to nest in holes in trees, or nest boxes (Bellrose &
Hepp 2011). Wood ducks or Aix sponsa, which in Latin means a water bird in bridal dress, are
one of the most brilliant species of birds in North America (Haramis n.d.). Males are brown and
green where the female bird is a grey-brown color. Wood ducks are mostly found in the United
States and they are a freshwater species that occupy all forest associated with fresh water
wetlands. This is in large part because the surrounding forest provides food and nest sites for
them. Wood Ducks thrive in wooded swamps where they nest in holes in trees, called cavities or
in nest boxes put up around lake margins (EPA 2012).
Habitat. The Wood Duck is the only North American duck that regularly produces two broods in
one year. Wood Ducks thrive in bottomland forests, swamps, freshwater marshes, and beaver
ponds and seem to fare best when open water alternates with 50-75% vegetative cover is
available so that the ducks can hide and forage for food in it (Bellrose and Hepp 2011). This
cover can consist of downed trees and shrubs (e.g., alder, willow, and buttonbush). Nesting
cavities can have openings as small as 4 inches across and cavity depths are variable, averaging
about 2 feet deep, but they can be as deep as 15 feet (Bellrose and Hepp 2011).
Wood Ducks nest in trees near water, sometimes directly over water, but other times up to halfmile away from the water (Cornell Lab of Ornithology 2012). After hatching the ducklings
jump down from the nest tree and make their way to water. The mother calls them to her, but
does not help them in any way. The ducklings may jump from heights of up to 89 m (290 ft)
without injury. A female wood duck lays one egg a day until the clutch is complete. The
average clutch size for the wood duck is 12 eggs; there can be as few as 6 and as many as 15
eggs, sometimes 30 to 40 eggs are laid in a nest (Cornell Lab of Ornithology 2012). This is not
4
uncommon it is a result of more than one female laying eggs in the same nest, a behavior called
intraspecific nest parasitism, dump nesting, Egg-dumping or intraspecific brood parasitism. This
is common in wood ducks and unfortunately cannot be effectively incubated and subsequently
fail. Females visit other wood ducks cavities, lay eggs in them, and leave them to be raised by
the other females. This may have been made more common by the abundance of artificial nest
boxes. In some areas it happens more. The Journal of Wildlife Management reported that out of
202 nests, 120 of them were classified as a dump nests box. It also reports that hatchability of
eggs in dumps nests are lower than that of eggs hatched in normal nests (Morse and Wright
1969). Depending on the weather the incubation time ranges from 27 to 37 days and starts after
the last egg is laid (Cornell Lab of Ornithology 2012). The average survival for wood ducks is
estimated at about 40%, with the greatest mortality occurring during the first two weeks after
leaving the nest (Haramis n.d.). Wood ducks will nest in dead timber but prefer cavities in trees.
After hatching in their tree wood ducks are precocial which means that they are mobile and ready
to find food. The mother calls to her babies within the first 26 to 36 hours after they have
hatched and they exit cavities which can be as high as 65 feet above the ground by free-falling to
earth (Cornell Lab of Ornithology 2012). In 63 to 70 days after the wood ducks are born they are
able to fly. Usually, wood ducks have one brood per season, but in the warmer climates of the
south there have been two broods reported (Cornell Lab of Ornithology 2012).
Population status and management. Wood ducks were one of the most popular game ducks;
abundant all over the United States and common in game markets. During the 19th century
uncontrolled forest clearing and hunting threatened wood duck populations and they were driven
almost to extinction (Haramis n.d.). The need for lumber and open land for agriculture destroyed
much prime wood duck habitat, especially old growth timber that provided nesting sites for
5
wood ducks. Because of this, ornithologists were predicting extinction for the species. Habitat
loss and unregulated hunting near the turn of the century made the public support and protect the
wood ducks with the International Migratory Bird Treaty of 1916 and of the Federal Migratory
Bird Treaty of 1918. This protected wood ducks from illegal hunting and the species made a
remarkable comeback (Haramis n.d.).
Over the next couple of decades the wood duck has recovered to become one of our most
abundant game ducks, largely due to the erection of artificial nest boxes. However, we continue
to see a shift where bottomlands are being logged off and converted back into farmlands, also
timber harvesting is also become a new problem for the wood ducks. Foresters hope that
landowners can be proactive in leaving bands of hardwoods about 55 yards wide along streams
and rivers to help the wood ducks habitat grow (Bromley et al. 2009). New ponds or wetlands
can also be developed in wooded drainages to attract waterfowl like the wood duck. Land
owners need to divert water from streams or catch runoff and spring water behind earthen dams.
These should be shallow and should contain one or more small islands. If it is a newly flooded
area it may not have the right aquatic vegetation and may not attract wood ducks right away, so it
must develop for several years to establish water plants for food and cover (Bromley 2009).
Wood Duck Reproduction
Wood ducks have ecological ties to beavers, that help create wetlands, and to woodpeckers
because they nest in the cavities that they create. Wood ducks require adequate nutrition for egg
laying, trees that have cavity nest sites and a daily roosting habitat (Haramis n.d.). Wetlands or
flooded bottomland is a ripe habitat for wood ducks because it has all three of these needs for
successful nesting (Haramis n.d.). Wood ducks make use of all types of wetlands, even small
6
brooks or water supplies. They are known to inhabit areas that are affected by development or
are heavily populated (Haramis n.d.).
During the fall and winter wood ducks eat seeds such as acorns or other nuts, fruits, insects, and
arthropods that are high in fat to carry them through the harsher months. Female wood ducks
change their diets to a higher percentage of aquatic insect life to meet protein demands during the
breeding period (GDNR 2002). When wood ducks choose a mate it begins in the fall until they
pair up in January. Male wood ducks claim a small area around the female, an activity called
mate-guarding, and the pair becomes monogamous for the rest of the breeding season; the male
remains with the female until the eggs are ready to hatch and then leaves the female (Cornell Lab
of Ornithology 2012). Unlike other ducks, female wood ducks breed during their first year with
most birds arriving at the breeding grounds in the spring are already paired up with a mate. They
are ready to breed as soon as the ice melts which can be as early as January in the South, and is
around the second week in April in the northern regions, such as Canada. Nesting tends to slow
down in June with only a few hatches extending into July in the north and into August in the
south (Cornell Lab of Ornithology 2012).
Nest boxes. Wildlife biologists determined that wood ducks would use manmade nesting boxes
and thousands were erected across the United States as old abandoned farmlands started to
become forests again (Bromley 2009). Handmade wood duck boxes should not be made from
treated lumber and should be placed so there is a 40 foot flight line in front of the box that is free
from any obstructions such as tree limbs or bushes. The boxes should be slightly tilted forward
so that it is easier for the ducklings to climb out and should be placed one per acre on suitable
brood rearing habitat (GDNR 2002). Do not place more than one box per post because this may
increase the possibility of fighting among nesting birds or “dump nesting” (Bromley 2009). It is
7
better to install nests on poles out in the water rather than on trees on land to help lower the
chance of predators. The nesting box should be at least 4 feet above water level and have a
predator guard installed around the post (GDNR 2002).
Once the wood duck box has been erected it should be lined with 4 inches of wood shavings and
checked or cleaned annually prior to the nesting season (GDNR 2002). Nest boxes located in the
open water are used more than boxes in heavily wooded areas. Birds hatched in nest boxes tend
to choose nest boxes rather than cavities in trees for nesting (Bromley 2009). Research shows
that 96% of wood ducks returned to the same area the next year where only 2% changed nest box
types (Semel and Sherman 1995). This is an imprinting behavior, so a landowner with a
successful nest box program will develop a breeding flock of ducks that return every year. When
you have established this you can then erect more nest boxes for the wood ducks (Bromley
2009).
In one study researchers compared two ways of positioning nest boxes for wood ducks (Semel
and Sherman 1995). One area they erected wood duck boxes on posts over water and in the
adjacent area boxes were mounted singly on trees in deciduous woodlands. The boxes that were
more visible or “traditionally placed” were more parasitized than the non-traditionally placed
boxes (Semel and Sherman 1995). Within the next four year the parasitism rates tripled among
the traditionally placed boxes and remained low among the non-traditional boxes (Semel and
Sherman 1995). Parasitism was highest early in the nesting season and showed that current
management practices combined with high population inflate parasitism rates. Their results
showed that a clear relationship between nest box placement and frequency of brood parasitism
exists. Nest box placement can significantly affect clutch size, rates of brood parasitism and egg
hatchability (Semel and Sherman 1995). If there is extreme brood parasitism it reduces the
8
reproductive efficiency, suggesting that nest boxes be distributed in sites that are inconspicuous
from the wetland and the entrance of the hole be faced away from open water, so that local wood
duck populations will more likely achieve their full reproductive potential (Semel and Sherman
1995). The frequency of brood parasitism in visible boxes increased yearly, but parasitism
remained relatively constant in the hidden wood duck boxes (Semel and Sherman 1995).
Current Study
Study site. The Cache River State Natural Area is located in the southernmost part of Illinois. It
has a floodplain that was carved long ago by glacial floodwater of the Ohio River (IDNR 2012).
The Cache River meandered across the rich wetlands and is home to massive cypress trees that
exceed 40 feet in circumference and are more than 1,000 years old (IDNR 2012). Engineers
bisected the Cache River in half in 1913 separating it into two parts the Upper Cache River
(UCR) from the Lower Cache River (LCR). The LCR, which is now considered the northern
most swamp, is now a great habitat for wood ducks to nest. The Cache River State Natural Area
is home to some of the highest quality aquatic and terrestrial or natural communities in Illinois
(IDNR 2012). Wetlands within this area are so important to migratory waterfowl that in 1996
the RAMSAR Convention designated the Cache River as the 19th wetland in the United States to
be declared as a Wetland of International Importance (IDNR 2012). The Cache River State
Natural Area totals 14,791 acres in Johnson, Massac and Pulaski counties and is home to many
water fowl including wood ducks (IDNR 2012).
Objectives. My first objective is to determine the best orientation of wood duck boxes. I
hypothesize that wood ducks will preferentially inhabit nest boxes facing away from open water.
I feel this would reduce the risk of dump nesting and help hatchling survival rates because
female wood ducks would not dump their eggs into other wood ducks boxes already inhabited by
9
a nesting female. This type of behavior is known as dump nesting and lowers survival rate
among broods. My second objective is to determine the best placement of wood duck boxes to
decrease predation risk. I hypothesize that putting wood duck boxes over open water will
decrease predation.
METHODS
I will monitor wood duck boxes in the CRW during the week of June 18th to the 23rd, when they
should be nesting. I will visit 100 wood duck boxes. I will record which boxes are inhabited, as
well as their orientation (i.e., facing open water or not) and location (i.e., over water or in the
woodland). I will also record if the nest boxes have been predated or likely subject to brood
parasitism rate.
Variables measured
Orientation and location. Cache River State Natural Area is composed of three units - Little
Black Slough, Lower Cache River Swamps and Glass Hill. The Little Black Slough Unit
surrounds the UCR. Heron Pond, a shallow wetland dominated by cypress and tupelo trees lies
in this bottomland forest. The LCR Swamps spread across a wide, flat floodplain and the
swamps are deep, open waters with ancient thick-buttressed cypress trees. This portion of the
Lower Cache River is known as Bottomland Swamp. The Glass Hill Management Unit occurs
about 3 miles north of Bottomland Swamp.
Habitation. Out of these sections we will be checking 100 wood duck boxes in four of the
sections. The two upland sites are Herrin Pond and Boss Island and the two lower land sites are
Bottomland Swamp & Section 8. I am going to check 25 wood duck boxes at each of the four
sites totaling 100 wood duck boxes in all. All of the wood duck boxes have been mounting so
10
that they are facing east or towards the water. I will check all 100 wood duck boxes to see if
there are signs of dump nesting or predation.
Predation and brood parasitism. If the eggs have been disturbed, broken or lower in number
then I will know that it is a result of predation. If there are extra eggs in the nest then I know that
the nest has been a victim of dump nesting. The eggs have been marked so that you will know
how many have been stolen or added by a new wood duck. I will then take that day’s results and
compare them to Doug’s previous results to see if in that week any predation or dump nesting
has occurred.
Analysis
When looking at Table 1, I will record what Doug has found the week prior when he checked the
wood duck boxes in the 1st check box and then I will record my results on the 2nd check box side
when I visit the wood duck boxes June 18-23. I will compare, on Table 1, the 1st check box and
2nd check box to see which wood duck boxes have been disturbed by predation or victim to dump
nesting.
Table 1. Data collection table1
Wood Duck
Box ID #
Facing
Water
Hypothesis 1
Inhabited
Inhabited
(1st check) (2nd check)
Over
Water
Predated
(1st check)
Hypothesis 2
Parisitized
Predated
(1st check) (2nd check)
Parisitized
(2nd check)
001
002
003
004
005
006
1
Each box will receive a 1 (no) or a 2 (yes)
11
REFERENCES
Bellrose, F.C. and Hepp, G. R. (2011). "Wood Duck." Wood Duck, Life History,Web. 01 Mar.
2012. Available online at http://www.allaboutbirds.org/guide/wood_duck/lifehistory/ac.
Bromley, P., Buhlmann, K., & Helfrich., L (2009). Management of Wood Ducks on Private
Lands and Waters. Available online at http://www.ext.vt.edu
Cornell Lab of Ornithology. (2012). Wood Duck Available on line at
http://www.birds.cornell.edu/nestinginfo/bios/sp_accts/wodu
Georgia Department of Natural Resources Wildlife Resources Division (GDNR). (2002). Wood
duck fact sheet. Available online at http://www.georgiawildlife.com/node/1296
Haramis, G. (No Date). Wood Duck Aix Sponsa. U. S. Fish and Wildlife Service Patuxent
Wildlife Research Center Laurel, Maryland. Available online at
http://www.dnr.state.md.us/irc/docs/00000260_15.pdf
Illinois Department of Natural Resources (IDNR). (2012). Cache River. Available on line at
http://dnr.state.il.us/lands/landmgt/parks/r5/cachervr.htm
Morse, T. & Wight, H. (1969). Dump nesting and its effect on production in wood ducks.
Journal of wildlife management, 33(2), 284-293
Semel, B. & Sherman, P. (1995). Alternative Placement Strategies for Wood Duck Nest Boxes.
WildlifeSociety Bulletin, 23(3), 463-471
United States Environmental Protection Agency (EPA). (2012). Available online at
http://water.epa.gov/type/wetlands/
12