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Sex determination in the Lesser Flamingo (Phoenicopterus minor) using morphological measurements

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Morphological measurements and blood samples were taken from 154 Lesser Flamingos Phoenicopterus minor, including adults (>3 years old), immature sub-adults (2–3 years old) and first-year juvenile birds of both sexes, captured at Lake Bogoria, Kenya (0°11'–20' N, 036°06' E) during 2001 and 2002. PCR amplification of the CHD-Z and CHD-W genes using DNA extracted from the blood samples was used to determine the sex of each bird. There were significant differences in mass and tarsus length among the three age groups, indicating that Lesser Flamingos continue to grow in skeletal size and mass between fledging and the attainment of adult plumage at 3–4 years of age. On average, males were significantly larger than females in all age groups, although there was substantial overlap between the sexes in all morphological measurements. The element with the least amount of overlap was head-and-bill length. Discriminant functions utilising head-and-bill length that correctly predict the sex of juvenile and immature birds with approximately 93% accuracy are presented. By adding total tarsus length, the sex of wild adult Lesser Flamingos is correctly predicted with approximately 98% accuracy. The same discriminant function developed for wild adult birds predicted the sex of 19 captive adult Lesser Flamingos of known sex with 100% accuracy.
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OSTRICH
ISSN 1727–947X
Ostrich 2005, 76(3&4): 148–153
Printed in South Africa — All rights reserved
Sex determination in the Lesser Flamingo (Phoenicopterus minor) using
morphological measurements
Brooks Childress1,2,3*, David Harper1, Baz Hughes2and Colin Ferris1
1Department of Biology, University of Leicester, Leicester LE1 7RH, United Kingdom
2Species and Populations, The Wildfowl and Wetlands Trust, Slimbridge GL2 7BT, United Kingdom
3Department of Ornithology, National Museums of Kenya, PO Box 40658, Nairobi, Kenya
* Corresponding author, e-mail: Brooks.Childress@wwt.org.uk
Morphological measurements and blood samples were taken from 154 Lesser Flamingos Phoenicopterus minor, including
adults (>3 years old), immature sub-adults (2–3 years old) and first-year juvenile birds of both sexes, captured at Lake
Bogoria, Kenya (0°11’–20’ N, 036°06’ E) during 2001 and 2002. PCR amplification of the CHD-Z and CHD-W genes using
DNA extracted from the blood samples was used to determine the sex of each bird. There were significant differences in
mass and tarsus length among the three age groups, indicating that Lesser Flamingos continue to grow in skeletal size and
mass between fledging and the attainment of adult plumage at 3–4 years of age. On average, males were significantly larger
than females in all age groups, although there was substantial overlap between the sexes in all morphological measure-
ments. The element with the least amount of overlap was head-and-bill length. Discriminant functions utilising head-and-bill
length that correctly predict the sex of juvenile and immature birds with approximately 93% accuracy are presented. By
adding total tarsus length, the sex of wild adult Lesser Flamingos is correctly predicted with approximately 98% accuracy.
The same discriminant function developed for wild adult birds predicted the sex of 19 captive adult Lesser Flamingos of
known sex with 100% accuracy.
The ability to correctly determine the sex in monomorphic
birds is critically important to research into sex-based sur-
vival analyses (e.g. Lens et al. 1998) and certain aspects of
avian behaviour such as mate choice (e.g. Childress and
Bennun 2002). It is also important in successfully managing
captive birds (Millar et al. 1997). For example, in managing
captive flocks of Lesser Flamingos, reproductive success
requires large flocks with a balanced sex ratio (Kear and
Duplaix-Hall 1975). Like all flamingo species, the Lesser
Flamingo (Phoenicopterus minor) is sexually monomorphic
(Studer-Thiersch 1986) (i.e. it is not possible to determine
its sex definitively through external observation, except by
observing mating behaviour at breeding sites). Although
male Lesser Flamingos are significantly larger than females
on average, large females and small males of similar age
make sex determination uncertain.
The sex of birds can be determined by several methods:
laparoscopy (Bush 1986, Richter et al. 1991), analysis of
hormone levels in blood samples, DNA analysis (Griffiths et
al. 1998, Fridolfsson and Ellegren 1999, Tomasulo et al.
2002) and faecal steroid analysis during the breeding peri-
od (Czekala and Lasley 1977, Bercovitz et al. 1978).
However, these methods are time-consuming, intrusive and
require extensive laboratory equipment and specialised
knowledge, and some methods may not work at all with ju-
venile flamingos (Van Couteren and Verheyen 1988). Field
researchers and aviculturists require a method for sexing
Lesser Flamingos that is simple and accurate.
Previous attempts have been made to use morphological
measurements to determine the sex of three species of
flamingo: Greater Flamingo Phoenicopterus roseus (Studer-
Thiersch 1986, Richter and Bourne 1990), Chilean Flamingo
Phoenicopterus chilensis (Van Couteren and Verheyen
1988, Richter et al. 1991) and Caribbean Flamingo
Phoenicopterus ruber (Richter et al. 1991). Only Van
Couteren and Verheyen (1988) used discriminant analysis.
The other attempts confirmed the mean size differences be-
tween males and females, and the overlap in measurements
between smaller males and larger females, but did not pro-
vide methods for reliably predicting the sex of new birds.
This study uses discriminant analysis of Lesser Flamingo
morphological measurements to determine whether it is pos-
sible to provide simple discriminant functions using one or
more of these measurements to correctly predict the sex of
Lesser Flamingos with a high degree of accuracy.
Methods
One hundred and fifty-four adult Lesser Flamingos, includ-
ing adults, immature birds and juvenile birds of both sexes
(Table 1) were captured at Lake Bogoria, Kenya in 2001
and 2002, using a trapping method developed specifically
for Lesser Flamingos (Childress et al. 2004). Age classifica-
tions were determined using plumage, skin and eye colour
descriptions in Zimmerman et al. (1999).
Five common morphological measurements (mass, flat-
tened wing length, total tarsus length, head-and-bill length
and culmen length) were taken. Mass was measured to the
nearest 20g on a Salter Electro Samson digital scale by
folding the legs, wrapping the bird in a cloth to temporarily
Introduction
Ostrich 2005, 76(3&4): 148–153 149
immobilise the legs and wings, and placing the wrapped
bird in a sling attached to the scale. Flattened wing length,
the measurement from the outer bend of the carpal joint (in-
cluding the skin and feathers) to the tip of the longest pri-
mary — with the wing flattened and the edge of the wing
and longest primary straightened against a measuring
board (Baker 1993) — was determined using a measuring
board that could accommodate flattened wings up to
480mm in length. Total tarsus length — the distance from
the posterior junction of the tibia (tibiotarsus) and the tarsus
(tarsometatarsus) folded to a right angle and including the
skin to the distal junction of the tarsus at the base of the
middle toe (Dzubin and Cooch 1992) — was taken with a
300mm butted wing rule. The butt was placed firmly at the
junction of the tibia and the tarsus, the foot was folded at a
right angle to the tarsus, and the measurement was deter-
mined to the nearest millimetre. Head-and-bill length — the
distance from the external occipital ridge at the back of the
head to the tip of the bill, including skin and feathers (Baker
1993) — was determined to the nearest tenth of a millime-
tre with a Vernier caliper. Culmen length — the distance be-
tween the bottom of the V-point where the horny portion of
the upper mandible meets the integument, and the tip of the
mandible (Dzubin and Cooch 1992) — was determined to
the tenth of a millimetre with a Vernier caliper.
The measurements were all taken by the same re-
searcher, to minimise observer bias. A blood sample from
the brachial vein was collected from each bird in a 50µl
capillary tube following a simple puncture with a 23-gauge
(0.6mm) needle. The blood samples were preserved in a
90% ethanol solution, following Dawson et al. (1998), and
stored in 2ml micro tubes.
The sex of each bird was determined through PCR (poly-
merase chain reaction) amplification of the CHD-Z and
CHD-W genes, using DNA extracted from its blood sample,
following the protocol for nucleated whole blood in the
DNeasy™ Tissue Kit (Qiagen Ltd. 1999), and P2/P8
primers. Each reaction contained approximately 10ng of ge-
nomic DNA, 1µM of each primer and 0.25 units of Biotaq™
(Bioline) DNA polymerase in the manufacturer’s buffer
(20mM (NH4)2SO4, 75mM Tris-HCl pH 9.0, 0.01% (w/v
Tween), including 2.0mM MgCl2 and 0.2mM of each dNTP
(Dawson et al. 2001). The amplification was performed
using a Perkin Elmer GeneAmp PCR System 9700 thermal
cycler. The reaction profile was 94°C for 3min, then 40 cy-
cles of 94°C for 15sec, 48°C for 20sec and 72°C for 25sec,
followed by 72°C for 1min and 4°C for 30min (Dawson et al.
2001). The PCR products were visualised on 2% agarose
gels stained with ethidium bromide.
Data analysis was done with the MINITABTM statistical
package (Minitab Inc. 2003). Normality of distribution was
assessed using the Anderson-Darling test, while tests for
homogeneous variances included Bartlett’s test or Levene’s
test, depending on whether or not the distributions were
normal. All comparisons among sexes and age groups were
made with non-parametric tests (Kruskal-Wallis and
Wilcoxon rank sum test), as some individual data subcom-
ponents (e.g. immature male head and bill and tarsus
lengths) were not normally distributed and in some compar-
isons variances were not homogeneous. Discriminant func-
tion analysis was used as the most appropriate way of iden-
tifying male and female Lesser Flamingos, given several
biometric measurements of the individuals (Manly 1995).
This function is a standard component of all good statistical
programs for computers.
Results
Age polymorphism
There were significant differences in mass and total tarsus
length among the three age groups for both sexes (male
mass: H = 26.8, df = 2, P < 0.001; female mass: H = 30.0, df
= 2, P < 0.001; male total tarsus length: H = 11.8, df = 2, P <
0.01; female total tarsus length: H = 16.5, df = 2, P < 0.001;
Kruskal-Wallis tests, adjusted for ties; sample sizes in
Appendix 1) indicating that Lesser Flamingos continue to
grow in skeletal size and mass for a considerable period after
fledging. Males and females appear to add mass continuous-
ly until they gain their adult plumage (Appendix 1). Both
sexes reach adult skeletal size while still in immature
plumage, as we found no significant differences between the
total tarsus lengths of adults and immature birds (Appendix 1).
We found no significant differences between juvenile —
and immature flattened wing lengths in either males or fe-
males (Appendix 1). However, flattened wing lengths of
adult birds of both sexes were significantly longer than
those of immature birds, indicating that flight feathers don’t
reach adult length until the adult plumage moults.
There were no significant differences in head-and-bill
lengths or culmen lengths among the three different age
groups (Appendix 1), as these components attain adult size
prior to fledging.
Sexual dimorphism
Males had greater mass and longer tarsi than females in
all age groups, although the differences were not signifi-
cant for mass in immature birds or for total tarsus length in
juvenile birds (Appendix 1). Males had significantly larger
head-and-bill length, culmen length and flattened wing
length in all age groups.
Despite significant differences in the morphological meas-
urement medians between the sexes and age groups, there
was considerable measurement variation in each morpho-
logical component within the sex and age groupings, and
substantial overlap between the sexes and among the age
groups (Figure 1). Large females and small males occur
frequently, making sex determination uncertain, as the
sexes are alike in the colour of their plumage, bare skin
areas and eyes at the same age.
Sex determination
Measurements of the different morphological components
varied substantially in their ability to predict the sex of indi-
Table 1: Sample distribution by age and sex of Lesser Flamingos
captured at Lake Bogoria, Kenya, 2001–2002
Juvenile Immature Adult
<1 yr old 2–3 yrs old >3 yrs old
Male 5 22 42
Female 13 18 54
Childress, Harper, Hughes and Ferris150
JUVENILE
Mass
2
4
6
8
10
12
14 1145 1313
900
MASS (g)
Flattened wing length
IMMATURE ADULT
1 100 1 300 1 500 1 700 1 900 2 100 2 300 900 1 100 1 300 1 500 1 700 1 900 2 100 2 300 900 1 100 1 300 1 500 1 700 1 900 2 100 2 300
1414 1545 1533 1816
270 290 310 330 350 370 270 290 310 330 350 370 270 290 310 330 350 370
307.3 326.8 308.8 321.7 322.4 346.0
2
4
6
8
10
12
14
16
18
FLATTENED WING LENGTH
Total tarsus length
160 180 200 220 240 260 160 180 200 220 240 260 160 180 200 220 240 260
TOTAL TARSUS LENGTH (mm)
2
4
6
8
10
12
14
16
18
20 192.5 207.4 208.7 229.4 213.8 243.0
Culmen length
85 90 95 100 105 110 85 90 95 100 105 110 85 90 95 100 105 110
2
4
6
8
10
12
14
16
18
20
22
24 91.7 102.0 93.8 101.0 94.1 102.5
115 120 125 130 135 140 145 115 120 125 130 135 140 145 115 120 125 130 135 140 145
Head-and-bill length
HEAD-AND-BILL LENGTH (mm)
CULMEN LENGTH (mm)
2
4
6
8
10
12
14
16
18 121.9 137.0 124.2 133.4 124.2 135.5
FREQUENCY
Figure 1: Fitted normal curves describing data distribution for mass, flattened wing length, total tarsus, culmen and head-and-bill length by
age of male and female Lesser Flamingos captured at Lake Bogoria, Kenya, 2001–2002. Broken lines = females; solid lines = males; verti-
cal reference lines = means.
Ostrich 2005, 76(3&4): 148–153 151
vidual birds using discriminant function analysis. Mass
was the least reliable, by itself correctly predicting the sex
in only 79% of cases overall, and in only 65% of immature
birds (Table 2). Total tarsus length was 94% accurate in
predicting adult birds, but only 61% and 73% accurate
with juvenile and immature birds, respectively. The most
useful measurements for all age classes were
head–and–bill length and culmen length, correctly predict-
ing the sex in 93–94% of all age classes. A combination of
head–and–bill length plus total tarsus length correctly pre-
dicted the sex of 98% of the adult birds. Other combina-
tions did not improve the accuracy of head-and-bill length
as a predictor of sex.
In developing discriminant functions to be used by field
researchers and aviculturists to determine Lesser Flamingo
sex, we calculated separate functions for each age class,
as Lesser Flamingos continue to grow until they attain their
adult plumage. Because culmen length is included in the
measurement of head-and-bill length, and was found to
have highly significant positive correlations with
head–and–bill length in all age classes (e.g. adult males: r
= 0.89, P < 0.001, adult females: r = 0.87, P < 0.001), we
used only head-and-bill length for juvenile and immature
birds, and a combination of head-and-bill length + total tar-
sus length in the case of adults (Table 3).
For example, if the head and bill + total tarsus length for
an adult Lesser Flamingo were 135mm and 275mm respec-
tively, the two discriminant function values would be calcu-
lated as follows:
male: –711.19 + (9.17 x 135) + (0.74 x 275) = 730.26
female: –591.46 + (8.50 x 135) + (0.59 x 275) = 718.29
The bird would be classified as male, as the male equa-
tion gives the higher value. On the other hand, if the head–
and–bill and total tarsus length had been 125mm and
210mm, the bird would be classified as female, because the
female equation would result in the higher number (594.94
vs 590.46).
The proposed discriminant functions correctly predicted the
sex of all 19 Lesser Flamingos in a captive flock of known sex.
The addition of mass to the discriminant functions resulted in a
complete failure to accurately predict the sexes of the captive
birds, identifying all birds as males. The reason was that the
captive birds were significantly lighter than their wild counter-
parts (male mean weights: 1 430g vs 1 780g, –14.3%, W = 1
207, P < 0.001; female mean weights: 1 180g vs 1 525g,
–17.5%, W = 2 064, P < 0.001, Wilcoxon rank sum tests).
Discussion
Despite being the most numerous of the world’s six flamin-
go species, with an estimated total population in Africa,
India and Pakistan of between 2.2 and 4.2 million
(Wetlands International 2002), the Lesser Flamingo is con-
sidered a near-threatened species because of its limited
number of breeding sites and its sporadic breeding pattern
(BirdLife International 2000). Very little is known about this
species, partly because it inhabits some of the most remote
and inhospitably hot areas of the globe, but also because
researchers have had no sure way of telling whether they
were recording the behaviour of males or females. This sit-
uation also exists with the other species of flamingo of the
genus Phoenicopterus (Studer-Thiersch 1986).
The study of the behaviour and ecology of any avian
species depends upon being able to distinguish male from
female. This is because the sex usually represents the
largest single division within a species and often corre-
sponds to important differences in both behaviour and ecol-
ogy (Griffiths and Tiwari 1993). Without being able to distin-
guish between the sexes, studies relating to sexual
dimorphism, for example, would be impossible (e.g.
Childress and Bennun 2002), as would studies of compara-
tive behaviour and ecology (e.g. Lens et al. 1998). In avicul-
ture, the ability to correctly identify the sexes is fundamental
to balancing and managing the breeding flocks (Kear and
Duplaix-Hall 1975).
On average, mean morphological component measure-
ments were significantly larger in males than in females for
all of the components measured. However, there was also
considerable variation in the measurements of each compo-
nent within each sex class, and measurement overlap be-
tween the sexes for all components, making sex determina-
tion uncertain. In addition, both skeletal size (as represented
by total tarsus length) and mass of recently-fledged juvenile
Lesser Flamingo males and females are significantly below
adult skeletal size and mass. Both sexes appear to stop
adding skeletal size (total tarsus length) while they are
still immature sub-adults, although they continue to add
mass until they attain their adult plumage at age three or
four (Childress et al. in press).
Total tarsus length, a prominent element in previously
proposed methods of determining the sex in other flamingo
Table 2: Percentage of correct sex predictions of Lesser Flamin-
gos captured at Lake Bogoria, Kenya, 2001–2002 by age class
and individual morphological component, based on discriminant
analysis.
Juv. Imm. Adult Total
Morphological element (%) (%) (%) (%)
Mass 78 65 85 79
Flattened wing length 78 75 85 82
Head-and-bill length 94 93 93 93
Culmen length 94 93 93 93
Total tarsus length 61 73 94 84
Head-and-bill + tarsus length 94 93 98 96
Table 3: Discriminant functions for predicting the sex of adult, im-
mature and juvenile Lesser Flamingos from morphological meas-
urements (hb = head–and–bill length, tt = total tarsus length). For
each bird of unknown sex, calculate the value of both functions for
its age group and determine the bird’s sex by the higher function
value.
Age groups Sex Discriminant functions
Adult Male –711.19 + (9.17 x hb) + (0.74 x tt)
Female –591.46 + (8.50 x hb) + (0.59 x tt)
Immature Male –442.07 + 6.63 x hb
Female –383.28 + 6.17 x hb
Juvenile Male –623.16 + 9.10 x hb
Female –493.14 + 8.09 x hb
Childress, Harper, Hughes and Ferris152
Received October 2004, accepted December 2004
Editor: MD Anderson
species (i.e. Greater, Chilean and Caribbean Flamingos),
was 94% accurate in predicting adult Lesser Flamingo sex,
but only 61% and 73% accurate with juvenile and immature
birds, respectively (Table 2). The elements with the least
overlap in all age classes — culmen length and head-and-
bill length — proved to be an accurate predictor of sex in
93–94% of all cases, regardless of age class. The head-
and-bill length is judged to be the easier measurement to
take consistently, as the start point for the culmen length
measurement — the V-point where the horny portion of the
upper mandible meets the integument — is less certain. By
combining total tarsus length and head-and-bill length in the
same discriminant function analysis, the accuracy of predic-
tion for adult Lesser Flamingos increased to 98% (94/96) in
wild birds and 100% (19/19) in captive birds. No increase in
accuracy was gained by adding total tarsus length for im-
mature or juvenile birds.
It is hoped that others involved in the study of flamingos
in the wild and in captivity will find this simple, accurate
method for determining the sex in Lesser Flamingos to be
useful with other flamingo species.
Acknowledgements — This study was conducted under the aus-
pices of the Department of Ornithology, National Museums of
Kenya, the Baringo and Koibatek County Councils, and William
Kimosop, Senior Warden, Lake Bogoria National Reserve, as part
of the Earthwatch Institute’s ‘Lakes of the Rift Valley’ research pro-
gramme. The Ministry of Education Science and Technology is
thanked for the granting of a research permit for the Earthwatch
work in Kenya. The authors thank the Earthwatch volunteers for
their assistance with the fieldwork and Mrs Velia Carn plus staff for
running the research camps. Field assistance was ably given by
Reuben Ndolo and James Njoroge.
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Appendix 1: Median morphological measurements by age group of male and female Lesser Flamingos captured at Lake Bogoria, Kenya,
2001–2002 (sample sizes in parentheses, ns = not significant at 0.05, results adjusted for unequal variances, Wilcoxon rank sum tests)
(Imm.: Juv.) (Ad.: Imm.)
Mass (g) Juv. Imm. W P Adult W P
Male 1 340.0 (05) 1 532.5 (22) 39.0 0.05 1 780.0 (42) 1 662.5 <0.001
Female 1 130.0 (13) 1 387.5 (18) 118.0 < 0.001 1 525.0 (54) 2 126.0 <0.05
Male % diff. +18.6 +10.5 +16.7
W 101.0 306.5 1 699.0
P <0.05 ns <0.001
Tarsus (mm)
Male 203.0 (5) 238.0 (22) 42.0 ns 242.5 (42) 1 469.0 ns
Female 185.0 (13) 210.0 (18) 138.5 <0.01 213.0 (54) 2 048.5 ns
Male % diff. +9.7 +13.3 +13.8
W 108.0 273.5 1 555.0
P ns <0.01 <0.001
Wing (mm)
Male 328.0 (05) 323.5 (22) 91.0 ns 347.0 (42) 1 767.0 <0.001
Female 309.0 (13) 307.0 (18) 207.5 ns 322.5 (54) 2 296.5 <0.001
Male % diff. +6.1 +5.4 +7.6
W 94.0 248.0 1 641.5
P <0.01 0.001 <0.001
Head-and-bill (mm)
Male 135.5 (5) 134.2 (22) 99.5 ns 135.5 (42) 1 461.0 ns
Female 120.8 (13) 124.2 (18) 168.0 ns 124.8 (54) 1 985.0 ns
Male % diff. +12.2 +8.1 +8.6
W 91.0 193.0 1 501.5
P <0.01 <0.001 <0.001
Culmen (mm)
Male 102.5 (05) 101.0 (22) 85.0 ns 101.9 (42) 1 466.5 ns
Female 91.5 (13) 93.7 (18) 166.0 ns 94.1 (54) 2 011.5 ns
Male % diff. +12.0 +7.8 +8.3
W 91.0 178.0 1 521.0
P <0.01 <0.001 <0.001
... To overcome this difficulty a range of techniques have been used such as laparoscopy (Petrides, 1950;Richter and Bourne, 1990;Richner, 1989), measuring the plasma testosterone levels during the breeding period (Czekala and Lasley, 1977;Bercovitz et al., 1978), vocalization analyses (Bourgeois et al., 2007), individual breeding or observation of territorial behavior (Castoro and Guhl, 1958;Flux and Innes, 2001;Fletcher and Hamer, 2003), and generalized molecular techniques (Griffiths et al., 1998;Bertault et al., 1999;Fridolfsson and Ellegren, 1999;Tomasulo et al., 2002;Dubiec and Zagalska-Neubauer, 2006;Balkız et al., 2007). However, despite the reliability and the large utilization of molecular techniques, these methods are time-consuming, intrusive and require extensive laboratory equipment, implying additional financial costs (Childress et al., 2005). ...
... As part of a long-term study on the reproductive biology of a colony of greater flamingos in Camargue, southern France (43 • 25 N, 4 • 38 E), a proportion of chicks were captured at the end of each breeding season (end of July-early August) and banded with a metal ring and a unique combination of plastic bands that allowed recognition of individuals. For each chick, only three external measurements were made (body weight, tarsus length and wing length; Childress et al., 2005) to avoid prolonged capture stress. Thus, between 1995Thus, between and 2008Thus, between (except for 2001Thus, between , 2002Thus, between and 2007, a total of 4013 Flamingos chicks were captured. ...
... Our results demonstrate that the sex of greater flamingo chicks can be determined based on individual morphology using DFA and a subsample of individuals molecularly sexed. This method was also used for adult greater flamingos (Richter and Bourne, 1990) and other birds, where morphometric criteria may discriminate between males and females (Childress et al., 2005;Alarcos et al., 2007;Hurley et al., 2007;Ackerman et al., 2008;Herring et al., 2008;Lislevand et al., 2009;Herring et al., 2010). ...
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We used a large dataset of greater flamingo chicks banded and measured at Camargue, France, to verify the applicability of discriminant function analysis to sex this species. Males and females sexed genetically differed significantly in all of the morphological characters measured (body mass, tarsus and wing length), with males being significantly larger than females. Although the discriminant rate varied substantially from one year to another, we found that it increased with the sample size of genetically sexed individuals. Our results suggest that discriminant function analysis (DFA) does not provide an efficient tool to sex greater flamingo chicks as these relationship are highly variable across years, requiring the genetic determination of sex on a large number of individuals every year for calibrating the DFA and still providing an overall low accuracy in sex determination. Indeed, conditions at breeding seasons can vary between years and can be considered proximate causes affecting the correct discriminant rate. Like previous studies, we recommend caution in dealing with discriminant equations computed from small datasets, and our simulation suggests that 325 genetically sexed individuals are needed to obtain 80 % correctly classified greater flamingo chicks.
... The external morphology cannot be used for sexing birds of monomorphic species, and differences in behavior between sexes are often restricted to the breeding season 5 . In these cases, the sex of birds can be determined by laparotomy 6,7,8 or molecular genetic analysis of blood or feather samples 9,10,11 . As an alternative to avoid destructive or invasive techniques, the use of external morphometrics to sex birds is of great value, being inexpensive and immediate in sex determination 12,13 . ...
... In particular, external measurements are used in discriminant function analysis (DFA) 14 to distinguish the sex of numerous taxa in the field 16,17,18,19,20,15 . In birds, the DFA has been effectively applied to a broad taxonomic range of species including: penguins 21,22 , divers 23 , petrels 24,25 , cormorants 26, 27 , vultures 28 , gulls 29 , skuas 30, 31 , moorhens 32 , rooks 33 , flamingos 34,11,12 , owls 35 and passerines 36 . ...
Article
Sexual dimorphism in birds may be expressed as differences in body size, plumage, color and/or behavior. Many species are monomorphic in color, making sex determination difficult in the field. An example of the latter are mockingbirds, which are passerines of the genus Mimus, endemic to the Americas. In order to distinguish between male and female mockingbirds using external body measurements that are easy to take, the objective of this work was to quantify morphometric differences between sexes in adults of the following species: M. thenca (45 specimens), M. patagonicus (95), M. saturninus (88), M. triurus (152), and M. dorsalis (7). We measured the following variables: culmen length, bill height and width, tarsus length, middle toe length, wing chord and tail length. Measurements were generally larger in males than in females except for bill width in M. saturninus and M. triurus, culmen length in M. thenca and M. dorsalis, and bill height in M. dorsalis. There were significant differences between sexes in wing chord for M. patagonicus, M. saturninus and M. triurus; tail length for M. patagonicus and M. triurus; tarsus length for M. patagonicus; and in middle toe length for M. triurus. No significant differences in measurements were found between sexes for M. thenca. Significant discriminant functions were obtained for M. patagonicus, M. saturninus and M. triurus, with a percentage of correct classification less than 80%. Only a few variables were useful for sex determination in the studied Mimus species, i.e. wing chord, tail length, middle toe length and tarsus length for three, two, one and one species, respectively.
... A monitoring program of ringed birds has been active throughout this period providing data that shed light on dispersal of native and foreign birds. (Childress et al. 2005). Two Discriminant Function Analyses (DFA) were developed for Glossy Ibis chicks born in Doñana (Figuerola et al. 2006) indicating substantial predictive value for tarsus length (or tarsus width) and, to a lesser extent, wing length. ...
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A review of ongoing projects focusing on the Glossy Ibis Plegadis falcinellus and carried out by the Laboratoire de Conservation des Zones Humides since 2002 is presented. A brief description of these projects (population counts, breeding ecology, foraging behaviour, niche partitioning, diet, dispersal, morphometric sexing, parasitology and conservation) and constraints hindering these efforts are provided and discussed. These projects have benefitted from a fruitful collaboration with Doñana Biological Station and it is expected that the recently created International Glossy Ibis Network may facilitate further collaboration that will ultimately help the conservation of the species across its breeding range.
... A monitoring program of ringed birds has been active throughout this period providing data that shed light on dispersal of native and foreign birds. (Childress et al. 2005). Two Discriminant Function Analyses (DFA) were developed for Glossy Ibis chicks born in Doñana (Figuerola et al. 2006) indicating substantial predictive value for tarsus length (or tarsus width) and, to a lesser extent, wing length. ...
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This is the first issue of the publication of the IUCN SSC Stork, Ibis and Spoonbill Specialist Group. The first issue is a Special Issue dedicated to the ecology and conservation of the Glossy Ibis Plegadis falcinellus. This has the participation of 75 researchers from various countries around the globe, and is the first monograph of the Glossy Ibis.
... The lesser flamingo is a long-legged social species of the family Phoenicopteridae that occurs in the western and eastern hemispheres, although it is more common in the eastern hemisphere. On average, males are significantly larger than females in all age groups, although with substantial overlap in all morphological measurements [52]; behavior does not differ between sexes [53]. Chest feathers of the macaw are yellow, and the wings are blue. ...
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Background and Aim: Many avian species are considered sexually monomorphic. In monomorphic bird species, especially in young birds, sex is difficult to identify based on an analysis of their external morphology. Accurate sex identification is essential for avian captive breeding and evolutionary studies. Methods with varying degrees of invasiveness such as vent sexing, laparoscopic surgery, steroid sexing, and chromosome inspection (karyotyping) are used for sex identification in monomorphic birds. This study aimed to assess the utility of a non-invasive molecular marker for gender identification in a variety of captive monomorphic birds, as a strategy for conservation. Materials and Methods: DNA was isolated from feather samples from 52 individuals representing 16 species of 11 families indigenous to both Indonesia and elsewhere. We amplified the chromodomain helicase DNA-binding (CHD) gene using polymerase chain reaction with MP, NP, and PF primers to amplify introns with lengths that differ between the CHD-W and the CHD-Z genes, allowing sex discrimination because the W chromosome is exclusively present in females. Results: Molecular bird sexing confirmed 33 females and 19 males with 100% accuracy. We used sequencing followed by alignment on one protected bird species (Probosciger aterrimus). Conclusion: Sex identification may be accomplished noninvasively in birds, because males only have Z sex chromosomes, whereas females have both Z and W chromosomes. Consequently, the presence of a W-unique DNA sequence identifies an individual as female. Sexing of birds is vital for scientific research, and to increase the success rate of conservation breeding programs.
... In many avian species, sex can be determined by observing plumage or sex-specific structural characteristics (such as colored soft tissue), sex-specific behavior or by measuring morphological characteristics (Jodice et al. 2000). However, this method cannot be applied to birds that are sexually monomorphic in both size and plumage (Coulson et al. 1983), making it necessary to use other methods such as anatomical examination (Richter et al. 1991) and genetic analysis (Childress et al. 2005). The use of external morphometrics to sex birds is of great value because it is inexpensive and allows a rapid and effective determination (Montalti et al. 2012). ...
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The objective of this study was to develop tools for distinguishing between sexes of the two Black-crowned Night-Heron (Nycticorax nycticorax) subspecies (N. n. obscurus and N. n. hoactli) using discriminant function analysis. Significant differences were found in length of the culmen, length of the bill from the gape, and length of the wing chord between the sexes of each subspecies, with males being larger than females. The resulting discriminant functions were able to differentiate between the sexes of each studied subspecies and between subspecies after determining the sex of the individuals (with a correct classification of 77.8% for females and 97.8% for males). In females, all morphometrics were greater for N. n. obscurus than N. n. hoactli; this was also the case for males, except for bill width, which was greater in N. n. hoactli. Wing chord length was the most useful measurement for constructing the discriminant functions. External morphometrics are a valuable tool not only for discriminating between N. n. hoactli and N. n. obscurus but also for sexing these subspecies.
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Waterbirds in stochastic environments exhibit nomadism in order to cater for the unpredictable availability of water resources. Lesser flamingos Phoeniconaias minor have long been thought to be nomadic waterbirds. In southern Africa, con-servation efforts for lesser flamingos are hampered by a lack of knowledge about their movement trajectories. To investigate their movement ecology in southern Africa, we fitted GPS–GSM transmitters to 12 adults and tracked their movements over four years, from March 2016 to February 2020. Net squared displacement (NSD) was used in nonlinear least squares models classifying trajectories as nomadic, migratory, mixed-migratory, home range restricted or dispersal movement types. Data from eight of the 12 birds met the criteria for the NSD analysis. Model success was good; only 8 out of 120 (6.7%) movement type models failed to reach convergence. Goodness of fit statistics from the NSD models supported migratory and mixed migratory movement types (concordance criteria coefficient (CC) = 0.78) for more than half of the annual trajectories investigated (57.2%). Dispersal, home range-restricted and nomadic movements best described 28.6, 9.5 and 4.8% of annual trajectories, respectively, but all resulted in a mean CC of < 0.4 and thus did not fit observed NSD pat-terns as well as the migratory movement types. We then used nonlinear mixed effects models to account for annual and individual differences in migration parameters. Variation in the timing and duration of all migrations were more important than variation in migration distance, indicating well-established summer and winter ‘ranges’ and routes between Kamfers Dam (South Africa) and Sua Pan (Botswana). We propose that lesser flamingos in central southern Africa may be partial migrants, not true nomads, as most of their movements followed a regular, repeated pattern between two primary locations. (PDF) Movement patterns of lesser flamingos Phoeniconaias minor: nomadism or partial migration?. Available from: https://www.researchgate.net/publication/343736462_Movement_patterns_of_lesser_flamingos_Phoeniconaias_minor_nomadism_or_partial_migration [accessed Aug 19 2020].
Article
Waterbirds in stochastic environments exhibit nomadism in order to cater for the unpredictable availability of water resources. Lesser flamingos Phoeniconaias minor have long been thought to be nomadic waterbirds. In southern Africa, conservation efforts for lesser flamingos are hampered by a lack of knowledge about their movement trajectories. To investigate their movement ecology in southern Africa, we fitted GPS–GSM transmitters to 12 adults and tracked their movements over four years, from March 2016 to February 2020. Net squared displacement (NSD) was used in nonlinear least squares models classifying trajectories as nomadic, migratory, mixed-migratory, home range restricted or dispersal movement types. Data from eight of the 12 birds met the criteria for the NSD analysis. Model success was good; only 8 out of 120 (6.7%) movement type models failed to reach convergence. Goodness of fit statistics from the NSD models supported migratory and mixed migratory movement types (concordance criteria coefficient (CC) = 0.78) for more than half of the annual trajectories investigated (57.2%). Dispersal, home range-restricted and nomadic movements best described 28.6, 9.5 and 4.8% of annual trajectories, respectively, but all resulted in a mean CC of < 0.4 and thus did not fit observed NSD patterns as well as the migratory movement types. We then used nonlinear mixed effects models to account for annual and individual differences in migration parameters. Variation in the timing and duration of all migrations were more important than variation in migration distance, indicating well-established summer and winter ‘ranges’ and routes between Kamfers Dam (South Africa) and Sua Pan (Botswana). We propose that lesser flamingos in central southern Africa may be partial migrants, not true nomads, as most of their movements followed a regular, repeated pattern between two primary locations.
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We determined hematologic parameters of five healthy and nine sick free-ranging Lesser Flamingos ( Phoeniconaias minor) from Lake Nakuru, Kenya. Heterophilia and lymphopenia were evident in sick birds, with up to 7.5-fold higher heterophil-to-lymphocyte ratio in sick birds compared to healthy birds. Leucopenia was present in a few sick birds. A higher than normal packed cell volume was observed in birds that had evidence of acute disease, whereas a lower than normal packed cell volume was seen in birds with evidence of prolonged sickness. Healthy birds had higher total white blood cell counts and lymphocyte counts and lower heterophil counts than zoo flamingos. Most sick birds were diagnosed with septicemia, occasionally with fibrinous exudation into the coelomic cavities. One bird had mycobacterial granulomas, one had a corynebacterium-associated wing abscess, and one had a wing fracture. We provide hematologic data for free-ranging Lesser Flamingos and compare the parameters of sick and healthy birds.
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Early attempts to identify sex in sexually monomorphic birds were based on morphological or chromosomal characters but since avian W-specific DNA sequences were identified, their PCR amplification has become commonly used molecular sexing method. We report here a DNA technique that amplifies an intrinsic CHD region without a DNA extraction. This test was applied to twelve species belonging to three waterbird orders, Ciconiiformes, Pelecaniformes and Phoenicopteriformes. All birds were sexed successfully with high reproducibility. There was complete agreement between our results and sex diagnosis by parallel methods. Because the proposed method eliminates the DNA extraction step, this protocol is more efficient and simple. It demands only minute amounts of DNA and reduces both time and the quantities of reagents consumed.
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Reproductive success and the intensity of five separate seasonal sexual characters, expressed similarly in both sexes and likely to be dependent on age and/or individual condition, were documented at a colony of great cormorants at Lake Naivasha, Kenya (00°46′ S, 36°22′ E) in 1996. The characters assessed were head filoplumes, thigh patch feathers, colour of cheek, neck and upper breast plumage, colour of gular skin, and colour of suborbital skin. More intensely developed sexual characters at the time of pair formation were associated with significantly earlier breeding. Pairs that bred earlier fledged significantly more chicks than those breeding later. However, correlations between the number of chicks fledged and the intensity of the parents’ sexual characters at pair formation were generally weak and not significant. An exception was the colour of the cheek, foreneck and upper breast plumage: males (but not females) with the darkest plumage in these areas fledged significantly more chicks than others. Correlations between paired male and female sexual character intensity were weak, and significant only in the case of suborbital skin colour. Other factors may have been more important than these characters in influencing mate selection.
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The black stilt Himantopus novaezelandiae is one of the world's rarest wading birds. There is at present a single population (approximately 70 birds) which comprises only 12 breeding pairs. Captive breeding and rearing are important short-term treatments which can be used in efforts to rescue a species from extinction. Captive breeding programmes have been developed and used for a number of New Zealand avian species, including the black stilt. However, as with many bird species, sex assignment in the black stilt is difficult. This difficulty has resulted in captive management problems, which include the need to identify same-sex pairs and the need to retain known-sex individuals as breeding stock. We present here a DNA-based method which can be easily used to sex both captive and wild black stilts. We describe how this method is presently being used to assist in the captive rearing programme and discuss the applications that this method may have for the conservation of this bird in the wild.
Article
The sex of 59 adult Greater Flamingos (Phoenicopterus ruber roseus L.) was determined by laparoscopic exam of the gonads. Concomitant body weight (kg) and linear measurements (mm) of the culmen (bill), tarsus, middle toe, and wing were taken and compared for males vs. females. Although an overlap between sexes existed in all measurements, males on average were larger than females. Student's t-test indicated significant sexual differences for all five measurements. Thus, weights and linear measurements—especially tarsus, middle toe, and wing length—appear to be a useful parameter in determining an individual's sex in lieu of laparoscopic, feather pulp, blood chromosome, or fecal steroid analysis.
Article
Gender was determined by laparoscopic visualization of the gonads for 38 adult American flamingos (Phoenicopterus ruber ruber L.) and 36 adult Chilean flamingos (P. chilensis L.). Concomitant body weight (kg) and linear measurements (mm) of the culmen (bill), tarsus (tarsometatarsus), middle toe, and wing were taken. Statistical comparisons of body weight and linear measurements for male vs. female were made for each species. Also, the same-sex statistical comparisons were made between these two species, and between each of these two species and with data for greater flamingos (P. r. roseas L.) from a previous publication. As previously published for greater flamingos, an overlap between sexes existed in all measurements with males on average larger than females for both American and Chilean flamingos. However, Students' t-test indicated a significant sexual difference for all measurements between males and females of each species except for culmen length in Chilean flamingos. Students' t-test also indicated a significant difference when species were compared (Chilean vs. greater, and American vs. Chilean) and subspecies (American vs. greater) were compared for most of the 5 measurements. Thus, despite limitations imposed by between-sex overlap, weights and linear measurements, especially tarsus, middle toe, and wing length, appear to be useful in determining an individual's gender when species or subspecies identification is considered.
Article
Molecular sexing is an attractive means to determine the sex of sexually monomorphic birds, e.g. chicks of most species. A universal approach for molecular sexing of birds would require that a conserved W chromosome-linked sequence could be analysed, but no single gene has previously been known from any avian W chromosome. The recent discovery of the CHD1W gene, apparently W-linked in all non-ratite birds, has opened new possibilities in this direction, although there is a problem in that the gene also exists in a very similar copy on the Z chromosome (CHD1Z). Here we describe a universal method for molecular sexing of non-ratite birds which is based on the detection of a constant size difference between CHD1W and CHD1Z introns. Using highly conserved primers flanking the intron, PCR amplification and agarose electrophoresis, females are characteriscd by displaying one (CHD1W) or two fragments (CHD1W and CHD1Z), while males only show one fragment (CHD1Z) clearly different in size from the female-specific CHD1W fragment. With one particular pair of primers (2550F and 2718R) we applied this test to 50 bird species from 11 orders throughout the arian phylogeny, successfully sexing 47 of the species. Using an alternative pair of primers, the three failing species could be reliably sexed. This means that a simple, rapid and cheap universal system for molecular sexing of non-ratite birds is now available.
Article
The sexes of non-ratite birds can be determined routinely by PCR amplification of the CHD-Z and CHD-W genes. CHD -based molecular sexing of four species of auklets revealed the presence of a polymorphism in the Z chromosome. No deviation from a 1:1 sex ratio was observed among the chicks, though the analyses were of limited power. Polymorphism in the CHD-Z gene has not been reported previously in any bird, but if undetected it could lead to the incorrect assignment of sex. We discuss the potential difficulties caused by a polymorphism such as that identified in auklets and the merits of alternative CHD -based sexing protocols and primers.