1. Black Vulture and its management in New Jersey
By: Carlos Olivares
Garrett Hess
2. 1
Table Of Contents
Executive Summary………………………………………………………………………………….2
Part 1: Introduction
1.1 Species description and
Taxonomy………………………………………………………………...2
1.2 Life History and Ecology…………………………………………………………………………….3
1.3 Population Status and Distribution………………………………………………………………....4
1.4 Current Threats to Population……………………………………………………………………....4
PART 2: CURRENT CONSERVATION/ MANAGEMENT EFFORTS
2.1 Management as a Whole…………………………………………………………………………....5
2.2 New Jersey Regulatory Protection………………………………………………………………....5
2.3 Habitat Conservation and Restoration……………………………………………………………..6
2.4 Public Outreach and Education…………………………………………………………………….6
2.5 Population Viability Analysis………………………………………………………………………..7
PART 3: CONSERVATION/ MANAGEMENT PLAN
3.1 Recovery Objectives…………………………………………………………………………………8
3.2 Conservation/ Management Strategy**...................................................................................9
STEPS
3.3 Discussing the Model………………………………………………………………………………..9
3.4 Future Prospects and Research…………………………………………………………………..14
PART 4: REFERENCES
LIST OF FIGURES
3. 2
EXECUTIVE SUMMARY
The Black Vulture (Coragyps atratus), is a Native raptor of the american region. Its range
extends from south of costa rica to just under massachusetts. Its usual habitat is woody
landscapes and can be found near bodies of water to roost. The species is hugely adaptable,
also being found in urban cities and disturbed habitats. Though its extensive range, much is still
unknown of the species in terms of their vital rates. For example, the general carrying capacity
is still widely unknown. The species is under no threat of extinction as the population is growing
exponentially. The Black Vulture is mostly considered a pest species, causing more human
discomfort than ecological distress. Black vulture accounts for many dollars in property damage
in the New Jersey as well as other densely populated areas. It tends to pick on the tops of black
roofs which later causes leaks entry points for smaller rodents. It also is a considerable noise
nuisance, which can interrupt the comfort of human settlements.
Current management options is using effigies (black vulture carcuses) in an upside down
position to potentially scare away the vultures several meters away from the property. Though
effective, the effigies decay away and so not quite efficient. We propose a management plan
that would decrease the population growth rate below the stable growth rate, by controlling the
survivorship of subadults and adults as suggested in the Elasticity model. After 5 years below
the stable growth rate, this management approach will be put on a pause to allow the population
to regain itself to a stable growth rate of 1. Once there, close watch will be appointed to make
sure the population does not rise again by relieving stress on subadult and adult survivorship.
We will measure the success of the management plan by surveying concentrated towns to see
if nuisance calls have decreased, property damage costs have decreased as well as overall
count of damage cause by the vultures have been mitigated. Managing the Black vulture is
crucial to the investment of infrastructure and to lower local economic spending on repairs and
the like.
PART 1: INTRODUCTION
1.1 Species Description and Taxonomy
The american Black vulture or Coragyps atratus is native raptor to the americas. It is part
of the Cathartidae family along with its common relative Turkey vulture (Cathartes aura). The
origin of its name stems from the greek word “coragyps” which means “raven-vulture”. The
species name “atratus” comes from latin which means “clothed in black”. Other names it goes
by is Urubu noir in french, Rabengeier in german and Zopilote negro in spanish. Other than the
north american black vulture, two other subspecies has been identified, with ranges smaller
than the prior and further down central and south america (www.hbw.com). The range of the
black vulture generally stretches from south america to south and east united states, though
increasing its range to the north. Body color is solid black, though white spots are common. The
bare skin of its head is also black and is considered to be warty in texture. Wingspan can reach
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from 137-150 cm. Body size can range between 60-68 cm. Its weight as an adult can range
from 1600g -2200g (allaboutbirds.org). As most birds, they have a type II survivorship curve,
which suggest survivorship is highest when it is young and lowers as it get older. Black vultures
can live up to 25 years old.
1.2 Life History and Ecology
In terms of habitat, the Black Vulture has been accustomed to disturbed habitats and
lives close to cities. Its home habitat is generally woodlands and can roost around areas of
water. It is fond of open lands which makes mountainous ranges attractive to the vulture. When
looking for food, it flies high in the sky with its family. It feed on carrion and forages near roads.
Common carrion that it likes range from cattle, donkeys, raccoons and skunks. It also can
depend on human discards and search through dumpsters for rotting vegetables. Though it
generally feeds on dead carcuses, it can sometimes feed on other bird and turtle eggs. Because
of its bad sense of smell, it relies on its relative--turkey vulture-- to guide it to possible food
sources.
It typically breeds within the woodlands and uses dark caves and crevices to nest. The
female can lay 1-3 eggs per clutch. It lays the pale green colored eggs directly on the ground.
Both male and female parents are present in the success of the offspring as they are
monogamous species and stay with one partner for most of their life. Incubation can take about
37-41 days (www.audubon.org). Once hatched, both parents feed the young by regurgitation.
Hatchlings can stay in the nest for another 60 days after that.
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Migration patterns tend to be very small. They can be found in areas of Cuba within the
winter months. Black vultures are considered resident to short distance migrants, moving
southward from there norma northward homes.
1.3 Population Status and Distribution
According to the IUCN, black vulture is considered “least concern” and not under threat
of being endangered. Due to the lack of studied information of the black vulture, the estimated
population size in the U.S. is generally still in question, however, rough estimates suggest there
are about 20 million birds within its wide range (www.iucnredlist.org). The population is above
the stable growth rate which suggest an increase in population is natural. The carrying capacity
of the black vulture is generally unknown and still a question of research. The population has
been increasing since 1966 and is continuing its increase today. Its range spreads across the
south of the U.S and can be found almost all over south america. Mountainous ranges are
generally unsuitable and tend to stay by the water.
1.4 Threats to Population? Reasons for Management
Based off the Population viability Analysis we conducted on the species, there is no
immediate threat of extinction within the next 100 years. The Black vulture does not have any
primary predators and thus are not burdened with population stress. Harvests are however
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allowed in New Jersey and may be the only negative effect on population size however
miniscule. There is no worry of over harvesting as the population is naturally growing above the
stable growth rate.
The main reason the Black vulture must be managed is due to elevated cost in property
damage as well as consistent nuisance reports. As an over-populated pest species, major
afflictions from the species are towards human beings and our settlements. Major problems are
towards infrastructure and roofs which they like to perch and roost.
PART 2: CURRENT CONSERVATION/ MANAGEMENT EFFORTS
2.1 Management as a whole
Currently management efforts are limited based on the Migratory Bird Act. The Act
protects black vultures from being harvested and managed. Often times the management of
black vultures is often times site specific. They can cause property damage to tarred roof tops
for local business, homeowners, and can cause a problem near airports which they can impact
takeoffs and landings of airplanes. The cause is typically due to the species congregating near
garbage.
Due to major concerns effigies have become the most common use of deterrence from
local businesses that is handled by the USDA’s Wildlife Services. The effigies are hanged
upside down that scares of black vultures. For roosting vultures they have been hazed with red
lasers. By far shooting is the most effective; however, this would be a disturbance to local
business owners and a permit would be needed because of the Migratory Bird Treaty Act of
1918 restrictions. Under the act it is considered illegal to kill this species without a permit.
2.2 New Jersey Regulatory Protection
Black vulture is not a harvested species in the state of New Jersey and is considered
least concern (LC) by the International Union for Conservation of Nature. The USDA Wildlife
Services in Robbinsville, NJ uses hanging effigies as the most widely used tactic to limit the
spread and reappearance of black vultures from roof stops, particularly tarred roof tops. The
species is considered a pest and there are no regulatory protection other than the Migratory Bird
Act which is the standard means of protection across the North American Continental.
2.3 Habitat Conservation and Restoration
The species is not threatened and there are no current habitat conservation or
restoration areas for its habitats. For nesting and roosting their habitats tend to be in cliffs or
areas that are away from human disturbance. With the increase in development and
infrastructure there are no known bird sanctuaries just for black vultures. However, if they are
injured they can be held in captivity based on the Migratory Bird Treaty Act of 1918, but it is still
7. 6
illegal to kill or possess a black vulture which otherwise can result in a fine of $15,000 or
imprisonment up to 6 months.
2.4 Public Outreach and Education
Wildlife consultation by wildlife professionals is the most common avenue of public
outreach and education. Homeowners who have tarred roof tops can pay for the services of a
wildlife professional. Site specific problems are the most common types of complaints:
homeowners, business owners, and farmers.
Through careful planning and proper procedures followed property damages can be
successfully resolved. It is suggested to have tarred roof tops painted a different color or to have
some type of structure to make it difficult for black vultures to land. For farmers it is suggested
that young calfs and newborns be kept in barns since black vultures have been known to kill
newborn farm animals that are vulnerable.
2.5 Population Viability Analysis
Based on Population Viability Analyses conducted there is neither an impending
extinction risk of the black vulture within 10 nor 100 years. The starting population was recorded
to be 15,000 starting individuals for the target number for management. The growth rate is 1.7%
to 1.6% annual increase.
With a management of reducing the starting population size to 15,000 it is noted that there is a
99% persistence and respectively an 1% chance of extinction. Within the graph generated it is
shown that the majority of the population remains under 1.5 million. There is distinctly more
variation in the model with a starting population of 15,000 which is our target number. There are
notable less simulations/lines at or above the 1.5 million population number. Most of the lines
are indicating that the population is under or fluctuating at a population of 500,000 individuals. It
takes longer for the simulation/lines to reach a majority of the trend lines to reach above 1
million individuals.
8. 7
Graph 1. PVA of 15,000 starting Population
However, with a higher starting population the extinction rate is zero and there is a
probability of 1 for existence. The original starting population which was determined was 18,350
for New Jersey, was determined from Pennsylvania population numbers of black vultures
through usage of state densities.
With a higher starting population there is a probability of zero for extinction and a probability of 1
for persistence with the growth rate of 1.7%. With the graph shown below it depicts that the
majority of simulations/lines do not take as long to converge at a certain population number,
notably at 1.2 million. There is also less fluctuation suggesting more certainty in the PVA. There
is also more lines converging on or over 600,000 individuals. By overall reducing the starting
population by 3350 individuals it takes longer for the simulations to converge on a certain
population number and there is more uncertainty in the pva model which is shown with the 1%
increase in the extinction rate. The overall mean lambda is held constant since black vulture
populations through studies have shown to increase by 1.7% to 1.6%.
9. 8
Graph 2. PVA of 18,350 starting Population
PART 3: CONSERVATION/ MANAGEMENT PLAN
3.1 Recovery Objectives
In order for the black vulture population to be effectively managed is through effort of
killing. Poisoning the population will have a negative externalities associated, as it may affect
any non targeted species that may try the bait. Continuation of current laws of black vulture
management will continue to be implemented. To be successful, population growth rate must be
driven below the stable growth rate. Once below, we then will propose the long term
management plan to keep the population stable around lambda of 1. To do this, we will ease the
stress of hunting subadult and adult populations that was initially used to decrease the overall
growth rate. A population of about 15,000 in New Jersey would be the ideal healthy population
size as it will decrease property damage in local areas as well as still be able to thrive. We will
propose killing to get the population from the estimated 18,350 in New Jersey to under just
15,000 within 4-5 years.
In terms of measuring its success, surveys will be conducted to cities and municipalities
to record any decreases in property damage as a whole. Nuisance call counts will also be
monitored to see if there has been any decreases.
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3.2 Conservation/ Management Strategy
The best possible option to manage black vulture will be to actively harvest them.
Poisoning through bait will risk negative externalities, harming non target species, thus affecting
their population rates. A grant proposal will be addressed to finance the plan in order for the
conservation effort to flow and be in effect immediately. Money will be spent on equipment gear
such as guns for hunters. Money from the grant will also provide pay for these hunters.
Another and most important aspect of the strategy is to win the approval of the public.
Seminars will be held in local communities to ensure engagement of the public and allow any
expressions of concern about the plan. Pamphlets and conservation information will be issued
as another media to communicate the importance of the plan. We will ask to collaborate with
national and non-profit conservation groups to further provide a support base. Given the timely
nature of engaging the public, this may take a few months to a year to effectively reach a
greater sense of local awareness.
After deliberation of money and communicating to local and state persons, the next step
is to implement the plan. Optimal habitats of the Black Vulture will be exploited to search for
adults within those areas. Killed birds will be collected and donated for effigy use to deal with
nuisance problems as the plan is put into effect. Birds will be manipulating the survival rates for
about 4-5 years to effectively hit our goal of 15,000 as timely as possible. After reaching our
goal, another conservation plan will be put in place to manage the population at lambda of 1. In
order to do this, the initial control of the population will be relieved slightly. Finally, we will
measure the success of the plan by surveys and measuring decreases in nuisance calls.
Addition to surveys and measuring nuisance calls, calculating property damage costs over the
years and noticing a decrease can assist in evaluation.
3.3 Discussing the Models
Here is the stochastic and variance matrix models:
Stochastic matrix model
Stage class
1 2 3 4
1 0 0
0.203833175
4
0.693418223
9
2
0.479753850
7
0 0 0
3 0
0.878330887
5
0.750933298
8
0
4 0 0
0.258755428
5
0.942840610
9
Table: Stochastic matrix model for Black Vulture
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Variance matrix
Stage class
1 2 3 4
1 0 0 0.25 0.25
2 0.25 0 0 0
3 0 0.15 0.15 0
4 0 0 0.1 0.12
Table: Variance for the Stochastic model
Graph: Average lambda over time
Graph: Total population over time
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The stochastic model shows the general distribution of fecundity and survivorship within
the stage classes of black vulture. Stage classes are defined as Egg( 0 years), Juveniles
(hatchlings to 2 years), Subadult(2 to 7 years), and Adults (8+ years) based off similar stage
structures suggested by Blackwell et al. in 2007. Black vultures do not become reproductive
until they are subadults (Blackwell 2007). Within the variance table, these numbers were chosen
arbitrarily to best described the species parameters. The mean lambda jumps from just under
1.25 and eventually stabilizes at about 1.12 after 5 years. Population of black vultures grow
exponentially. These measures justify the need for the conservation of Black vulture in New
Jersey.
Here is the elastic sensitivity model for the black vulture:
F(h) F(j) F(sa) F(a)
Eggs: 0 0 0.4987 0.4987
Juveniles 0.875 0 0 0
Subadults: 0 0.8905 0.657 0
Adults: 0 0 0.249 0.906
Table:Stage matrix for initial population
Year Hatchlings juvs Sub-Adults Adults Total lt
0 18870.0 22570.0 69005.0 74555.0 185000.0
1 71593.4 16511.3 65434.9 84729.1 238268.6 1.2879382
2 74886.8 62644.2 57694.0 93057.8 288282.8 1.209906811
3 75179.9 65525.9 93689.6 98676.2 333071.6 1.155364369
4 95932.8 65782.4 119904.9 112729.3 394349.5 1.183978018
Table: Age distribution and population at lambda= 1.18
Elasticity matrix
F(e) F(j) F(sa) F(a)
Eggs 0 0 0.1078987199
0.0809368886
2
Juveniles 0.2182708061 0 0 0
Subadults 0 0.1819029659 0.1568703163 0
Adults 0 0
0.0779654865
4
0.1761548167
Table: Elastic model for initial population
Given nothing is done to the population, the most weighted metric to contribute to the population
is the survivability of eggs that make it to the juvenile stage with a value of 0.218. The next best
metric is the survivability of a juvenile moving to the subadult stage with the value 0.182
following survivorship of subadults and adults with values 0.157 and 0.176 respectively.
Though it may be ideal to focus on this metric, it does not seem quite moral to affect the
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survivability of juveniles. Moreover, the conservation method may not be accepted in the public
which can sway the overall support of the plan. Population growth exceeds 1 by about 18%,
suggesting a high population increase.
Here is the proposed decrease in survivorship metric:
F(e) F(j) F(sa) F(a)
Eggs: 0 0 0.4987 0.4987
Juviniles 0.875 0 0 0
Subadults: 0 0.8905 0.251 0
Adults: 0 0 0.249 0.5
Table: Stage matrix for proposed plan of decrease
Year Eggs Juvenile Sub-Adults Adults Total lt
0 18870.0 22570.0 69005.0 74555.0 185000.0
1 71593.4 16511.3 37418.8 54459.7 179983.2 0.9728822
2 45819.9 62644.2 24095.4 36547.2 169106.6 0.9395688314
3 30242.4 40092.4 61832.6 24273.3 156440.8 0.9251013519
4 42941.0 26462.1 51222.2 27533.0 148158.4 0.9470575442
Table: Age distribution and population trend with lambda = 0.94
Elasticity matrix
F(e) F(j) F(sa) F(a)
Eggs 0 0
0.0841148998
9
0.0754900541
8
juveniles 0.1596049541 0 0 0
Subadults 0 0.1596049541 0.1991846008 0
Adults 0 0
0.0754900541
8
0.2465104828
Table: Elastic sensitivity model for proposed plan
With a decrease in subadult and adult survivorship to a value 0.199 and 0.247, the population
growth rate decreases from a lambda value of 1.18 (18% growth rate) to a lambda of 0.94(
0.06% growth rate decrease). At 4 years, the population decreases from its original population
size to about 14,800, which is just on range. At 3 years, population is above our goal and
allowed the extra year for proposed measure.
Here is the long term management proposal to maintain stable growth rate:
F(e) F(j) F(sa) F(a)
Eggs 0 0 0.4987 0.4987
Juveniles 0.875 0 0 0
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Subadults: 0 0.8905 0.371 0
Adults: 0 0 0.249 0.62
Table: stage structure matrix for long term management
Year Eggs Juveniles Sub-Adults Adults Total lt
0 1530.0 1830.0 5595.0 6045.0 15000.0
1 5804.9 1338.8 3705.4 5141.1 15990.0 1.0660022
2 4411.7 5079.3 2566.8 4110.1 16167.9 1.011123669
3 3329.8 3860.2 5475.4 3187.4 15852.8 0.9805113708
4 4320.1 2913.6 5468.9 3339.6 16042.2 1.011944373
5 4392.8 3780.1 4623.5 3432.3 16228.7 1.011626499
6 4017.4 3843.7 5081.5 3279.3 16221.9 0.9995810371
7 4169.5 3515.2 5308.0 3298.4 16291.2 1.004275892
8 4292.1 3648.3 5099.6 3366.7 16406.7 1.007088527
9 4222.2 3755.5 5140.8 3357.2 16475.7 1.004202918
10 4237.9 3694.4 5251.5 3361.5 16545.4 1.004230838
Table: age distribution and population at lambda= 1.004
Elasticity matrix
F(e) F(j) F(sa) F(a)
Eggs 0 0 0.1176537534
0.0761238577
2
Juveniles 0.2411698223 0 0 0
Subadults 0 0.2164086904 0.126667865 0
Adults 0 0
0.0850142813
5
0.1369617298
Table: Elasticity model for long term management plan
As shown, stress on the survivorship of subadults and adults are relieved slightly to
0.371 and 0.62 respectively. Starting population is assumed 15,000 and lambda recovers to a
stable growth rate 1.004 (0.004% increase). Though the population is a little above 1, current
management laws on black vulture management will keep population levels under control. Egg
to juvenile survivorship and juvenile to subadults are still the highest weighted vital rate to
contribute to the species population however still will prose social discomfort and risk of losing
support for conservation method.
3.4 : Future Prospects and research
As stated, much still needs to be found on reliable vital rates and carrying capacity of the
Black vulture. Ecology researchers may want to focus its efforts on the species due to its
influence on the human world. More knowledge of survivorships can be helpful to better assess
management plans that are more efficient. In terms of habitat and selection of roost, more study
