Morphometric Characteristic of Glandular Stomach and Gizzard of the Common Scoter Melanitta nigra (Aves, Anseriformes) Wintering on the Polish Baltic Coast
The material for studies were stomachs of 52 individuals of the Common Scoter Melanitta nigra obtained in winter in western parts of Polish Baltic coast. Six parameters of stomachs were established: glandular stomach weight (GSW) and length (GSL), gizzard length (GL) and width (GWi), combined length...
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Інститут зоології ім. І.І. Шмальгаузена НАН України
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irk-123456789-652522014-06-24T03:01:52Z Morphometric Characteristic of Glandular Stomach and Gizzard of the Common Scoter Melanitta nigra (Aves, Anseriformes) Wintering on the Polish Baltic Coast Dziala-Szczepanczyk, E. Морфология The material for studies were stomachs of 52 individuals of the Common Scoter Melanitta nigra obtained in winter in western parts of Polish Baltic coast. Six parameters of stomachs were established: glandular stomach weight (GSW) and length (GSL), gizzard length (GL) and width (GWi), combined length of both stomachs (GGL), and four measurements describing the birds’ body size: body weight (BW) and length (BL), sternum length (SL) and tarsus length (TL). Dimorphic differences connected with the birds’ sex and age in concerning average values of stomachs parameters and indices of their relative size were examined. Relationships among values of the stomach parameters and relationships between the values of the stomach parameters and the measurements describing the bird body size were analysed. Despite clearly marked sexual dimorphism in the bird body size in favour of males, only in three parameters GWi, GW, GGL, and in the index GGL/SL (both stomach length in relation to sternum length) drakes achieved significantly higher values than ducks. Adult and immature birds, both in the group of males and females, did not differ in body size and most average values of the stomach parameters. Only in the group of females adult individuals were characterised with heavier gizzard than immature individuals, and adult individuals of both sexes had wider gizzard than immature individuals. Except GSL and GSW, remaining parameters of the stomachs positively correlated with at least two body parameters of the birds. A positive correlation for the relation of GL to BL, TL, SL; GWi to BW, BL; GW to BW, BL; GGL to BW, TL, SL were shown. No relationship between GSL and gizzard measurements was noticed. But GSW was in a positive correlation with GWi and GW. Материалом для исследований послужили желудки 52 особей синьги Melanitta nigra, полученные зимой в западных районах польского побережья Балтики. Были определены 6 параметров желудков: масса (GSW) и длина (GSL) железистого желудка, масса (GW), длина (GL), ширина (GWi) мускульного желудкa и общая длина обоих желудков (GGL), а также 4 измерения, описывающие размеры тела птиц: масса (BW) и длина (BL) тела, длина грудины (SL) и длина цевки (TL). Исследовали диморфические различия, связанные с полом и возрастом птиц в объеме средних величин желудочных параметров и показателей их относительных размеров. Анализировали зависимости между величинами желудочных параметров и размерами тела птиц. Несмотря на четко обозначенный половой диморфизм по размерам тела птиц в пользу самцов, только по 3 параметрам GWi, GWL и GGL и по параметру GGL/SL (длины обоих желудков относительно длины грудины) селезни достигали действительно больших величин, чем утки. Птицы в возрасте adultus и immaturus как в группе самцов, так и самок не отличались размерами тела и в большинстве по средним величинам желудочных параметров. Только в группе самок взрослые особи характеризовались более тяжелым мускульным желудком, чем молодые, а взрослые особи обоих полов имели более широкий мускульный желудок, чем молодые. Кроме GSL и GSW остальные параметры желудков коррелировали положительно по крайней мере с двумя параметрами тела птиц. Определена положительная корреляция для связи GL c BL, TL и SL; GWi c BW и BL; GW c BW и BL; GGL c BW, TL и SL. Не обнаружена зависимость между GSL и измерениями мускульного желудка. Однако GSW находилась в положительной корреляции с GWi и GW. 2007 Article Morphometric Characteristic of Glandular Stomach and Gizzard of the Common Scoter Melanitta nigra (Aves, Anseriformes) Wintering on the Polish Baltic Coast / E. Dziala-Szczepanczyk // Вестник зоологии. — 2007. — Т. 41, № 3. — С. 257–265. — Бібліогр.: 38 назв. — англ. 0084-5604 http://dspace.nbuv.gov.ua/handle/123456789/65252 591.433;598.243.8(474) en Вестник зоологии Інститут зоології ім. І.І. Шмальгаузена НАН України |
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Морфология Морфология |
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Морфология Морфология Dziala-Szczepanczyk, E. Morphometric Characteristic of Glandular Stomach and Gizzard of the Common Scoter Melanitta nigra (Aves, Anseriformes) Wintering on the Polish Baltic Coast Вестник зоологии |
| description |
The material for studies were stomachs of 52 individuals of the Common Scoter Melanitta nigra obtained in winter in western parts of Polish Baltic coast. Six parameters of stomachs were established: glandular stomach weight (GSW) and length (GSL), gizzard length (GL) and width (GWi), combined length of both stomachs (GGL), and four measurements describing the birds’ body size: body weight (BW) and length (BL), sternum length (SL) and tarsus length (TL). Dimorphic differences connected with the birds’ sex and age in concerning average values of stomachs parameters and indices of their relative size were examined. Relationships among values of the stomach parameters and relationships between the values of the stomach parameters and the measurements describing the bird body size were analysed. Despite clearly marked sexual dimorphism in the bird body size in favour of males, only in three parameters GWi, GW, GGL, and in the index GGL/SL (both stomach length in relation to sternum length) drakes achieved significantly higher values than ducks. Adult and immature birds, both in the group of males and females, did not differ in body size and most average values of the stomach parameters. Only in the group of females adult individuals were characterised with heavier gizzard than immature individuals, and adult individuals of both sexes had wider gizzard than immature individuals. Except GSL and GSW, remaining parameters of the stomachs positively correlated with at least two body parameters of the birds. A positive correlation for the relation of GL to BL, TL, SL; GWi to BW, BL; GW to BW, BL; GGL to BW, TL, SL were shown. No relationship between GSL and gizzard measurements was noticed. But GSW was in a positive correlation with GWi and GW. |
| format |
Article |
| author |
Dziala-Szczepanczyk, E. |
| author_facet |
Dziala-Szczepanczyk, E. |
| author_sort |
Dziala-Szczepanczyk, E. |
| title |
Morphometric Characteristic of Glandular Stomach and Gizzard of the Common Scoter Melanitta nigra (Aves, Anseriformes) Wintering on the Polish Baltic Coast |
| title_short |
Morphometric Characteristic of Glandular Stomach and Gizzard of the Common Scoter Melanitta nigra (Aves, Anseriformes) Wintering on the Polish Baltic Coast |
| title_full |
Morphometric Characteristic of Glandular Stomach and Gizzard of the Common Scoter Melanitta nigra (Aves, Anseriformes) Wintering on the Polish Baltic Coast |
| title_fullStr |
Morphometric Characteristic of Glandular Stomach and Gizzard of the Common Scoter Melanitta nigra (Aves, Anseriformes) Wintering on the Polish Baltic Coast |
| title_full_unstemmed |
Morphometric Characteristic of Glandular Stomach and Gizzard of the Common Scoter Melanitta nigra (Aves, Anseriformes) Wintering on the Polish Baltic Coast |
| title_sort |
morphometric characteristic of glandular stomach and gizzard of the common scoter melanitta nigra (aves, anseriformes) wintering on the polish baltic coast |
| publisher |
Інститут зоології ім. І.І. Шмальгаузена НАН України |
| publishDate |
2007 |
| topic_facet |
Морфология |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/65252 |
| citation_txt |
Morphometric Characteristic of Glandular Stomach and Gizzard of the Common Scoter Melanitta nigra (Aves, Anseriformes) Wintering on the Polish Baltic Coast / E. Dziala-Szczepanczyk // Вестник зоологии. — 2007. — Т. 41, № 3. — С. 257–265. — Бібліогр.: 38 назв. — англ. |
| series |
Вестник зоологии |
| work_keys_str_mv |
AT dzialaszczepanczyke morphometriccharacteristicofglandularstomachandgizzardofthecommonscotermelanittanigraavesanseriformeswinteringonthepolishbalticcoast |
| first_indexed |
2025-07-05T15:43:53Z |
| last_indexed |
2025-07-05T15:43:53Z |
| _version_ |
1836822509408747520 |
| fulltext |
UDC 591.433;598.243.8(474)
MORPHOMETRIC CHARACTERISTIC OF GLANDULAR
STOMACH AND GIZZARD OF THE COMMON SCOTER
MELANITTA NIGRA (AVES, ANSERIFORMES)
WINTERING ON THE POLISH BALTIC COAST
E. Dzia/la-Szczepanń́czyk
Agricultural University, Judyma str., 20, Szczecin, 71–466 Poland
E-mail: ewa.dziala-szczepanczyk@biot.ar.szczecin.pl
Ïðèíÿòî 30 ÿíâàðÿ 2007
Morphometric Characteristic of Glandular Stomach and Gizzard of the Common Scoter Melanitta nigra
(Aves, Anseriformes) Wintering on the Polish Baltic Coast. Dzia/la-Szczepanń́czyk E. — The material for
studies were stomachs of 52 individuals of the Common Scoter Melanitta nigra obtained in winter in
western parts of Polish Baltic coast. Six parameters of stomachs were established: glandular stomach
weight (GSW) and length (GSL), gizzard length (GL) and width (GWi), combined length of both
stomachs (GGL), and four measurements describing the birds’ body size: body weight (BW) and length
(BL), sternum length (SL) and tarsus length (TL). Dimorphic differences connected with the birds’
sex and age in concerning average values of stomachs parameters and indices of their relative size were
examined. Relationships among values of the stomach parameters and relationships between the values
of the stomach parameters and the measurements describing the bird body size were analysed. Despite
clearly marked sexual dimorphism in the bird body size in favour of males, only in three parameters
GWi, GW, GGL, and in the index GGL/SL (both stomach length in relation to sternum length)
drakes achieved significantly higher values than ducks. Adult and immature birds, both in the group of
males and females, did not differ in body size and most average values of the stomach parameters. Only
in the group of females adult individuals were characterised with heavier gizzard than immature
individuals, and adult individuals of both sexes had wider gizzard than immature individuals. Except
GSL and GSW, remaining parameters of the stomachs positively correlated with at least two body
parameters of the birds. A positive correlation for the relation of GL to BL, TL, SL; GWi to BW, BL;
GW to BW, BL; GGL to BW, TL, SL were shown. No relationship between GSL and gizzard
measurements was noticed. But GSW was in a positive correlation with GWi and GW.
Key wo r d s: Common Scoter Melanitta nigra nigra, morphometry, glandular stomach (proventriculus)
ventriculus glandularis, muscular stomach (gizzard, ventriculus), ventriculus muscularis.
Ìîðôîìåòðè÷åñêàÿ õàðàêòåðèñòèêà æåëåçèñòîãî è ìóñêóëüíîãî æåëóäêîâ ñèíüãè Melanitta nigra
(Aves, Anseriformes), çèìóþùåé íà ïîëüñêîì ïîáåðåæüå Áàëòèêè. Äçÿëà-Ùåïàíü÷èê Å. — Ìàòåðèà-
ëîì äëÿ èññëåäîâàíèé ïîñëóæèëè æåëóäêè 52 îñîáåé ñèíüãè Melanitta nigra, ïîëó÷åííûå çèìîé
â çàïàäíûõ ðàéîíàõ ïîëüñêîãî ïîáåðåæüÿ Áàëòèêè. Áûëè îïðåäåëåíû 6 ïàðàìåòðîâ æåëóäêîâ:
ìàññà (GSW) è äëèíà (GSL) æåëåçèñòîãî æåëóäêà, ìàññà (GW), äëèíà (GL), øèðèíà (GWi)
ìóñêóëüíîãî æåëóäêa è îáùàÿ äëèíà îáîèõ æåëóäêîâ (GGL), à òàêæå 4 èçìåðåíèÿ,
îïèñûâàþùèå ðàçìåðû òåëà ïòèö: ìàññà (BW) è äëèíà (BL) òåëà, äëèíà ãðóäèíû (SL) è äëèíà
öåâêè (TL). Èññëåäîâàëè äèìîðôè÷åñêèå ðàçëè÷èÿ, ñâÿçàííûå ñ ïîëîì è âîçðàñòîì ïòèö â
îáúåìå ñðåäíèõ âåëè÷èí æåëóäî÷íûõ ïàðàìåòðîâ è ïîêàçàòåëåé èõ îòíîñèòåëüíûõ ðàçìåðîâ.
Àíàëèçèðîâàëè çàâèñèìîñòè ìåæäó âåëè÷èíàìè æåëóäî÷íûõ ïàðàìåòðîâ è ðàçìåðàìè òåëà
ïòèö. Íåñìîòðÿ íà ÷åòêî îáîçíà÷åííûé ïîëîâîé äèìîðôèçì ïî ðàçìåðàì òåëà ïòèö â ïîëüçó
ñàìöîâ, òîëüêî ïî 3 ïàðàìåòðàì GWi, GWL è GGL è ïî ïàðàìåòðó GGL/SL (äëèíû îáîèõ
æåëóäêîâ îòíîñèòåëüíî äëèíû ãðóäèíû) ñåëåçíè äîñòèãàëè äåéñòâèòåëüíî áîëüøèõ âåëè÷èí,
÷åì óòêè. Ïòèöû â âîçðàñòå adultus è immaturus êàê â ãðóïïå ñàìöîâ, òàê è ñàìîê íå îòëè÷àëèñü
ðàçìåðàìè òåëà è â áîëüøèíñòâå ïî ñðåäíèì âåëè÷èíàì æåëóäî÷íûõ ïàðàìåòðîâ. Òîëüêî â
ãðóïïå ñàìîê âçðîñëûå îñîáè õàðàêòåðèçîâàëèñü áîëåå òÿæåëûì ìóñêóëüíûì æåëóäêîì, ÷åì
ìîëîäûå, à âçðîñëûå îñîáè îáîèõ ïîëîâ èìåëè áîëåå øèðîêèé ìóñêóëüíûé æåëóäîê, ÷åì
ìîëîäûå. Êðîìå GSL è GSW îñòàëüíûå ïàðàìåòðû æåëóäêîâ êîððåëèðîâàëè ïîëîæèòåëüíî ïî
êðàéíåé ìåðå ñ äâóìÿ ïàðàìåòðàìè òåëà ïòèö. Îïðåäåëåíà ïîëîæèòåëüíàÿ êîððåëÿöèÿ äëÿ
Vestnik zoologii, 41(3): 257–265, 2007
© E. Dzia/la-Szczepan ´czyk, 2007
ñâÿçè GL c BL, TL è SL; GWi c BW è BL; GW c BW è BL; GGL c BW, TL è SL. Íå îáíàðóæåíà
çàâèñèìîñòü ìåæäó GSL è èçìåðåíèÿìè ìóñêóëüíîãî æåëóäêà. Îäíàêî GSW íàõîäèëàñü â
ïîëîæèòåëüíîé êîððåëÿöèè ñ GWi è GW.
Êëþ÷åâûå ñ ëîâ à: ñèíüãà, Melanitta nigra nigra, ìîðôîìåòðèÿ, æåëåçèñòûé æåëóäîê, ventricu-
lus glandularis, ìóñêóëüíûé æåëóäîê, ventriculus muscularis.
Introduction
A characteristic feature of the alimentary system in birds is the presence of two stomachs — the front
one — glandular stomach and the rear one — the muscular stomach (gizzard). Their shape and mutual size
proportions are characterised by interspecific variability and, to a lesser extent, intraspecific variability. The
former is a result of adaptation of individual species to taking and digesting food of a specific kind. Whereas
individual variability may be connected, among other things, with genetic and hormonal conditions, parasite
infections, amount and kind of available food (Ankney, 1977; McLeland, 1979; Duke, 1997). Anseriform
birds are an immensely varied ecological group. They represent all three trophic types — predatory,
omnivorous and herbivorous birds. Belonging to this order Common Scoter Malanitta nigra nigra (L., 1758)
is classified as a predatory bird. It represents tribe Mergini from a sub-family ducks Anatinae (del Hoyo et
al., 1992). It feeds by diving. The species has well developed both stomachs — glandular stomach and gizzard.
It nests in the taiga and winters on not freezing seas of Europe (del Hoyo et al., 1992). The species is
numerously migrating in Poland and winters on the Baltic (Tomia//lojc´, Stawarczyk, 2003).
The purpose of this study is to present a morphometric characteristic of both stomachs — glandular
stomach and gizzard — of wintering common scoters in relation to age, sex, and the birds’ body weight.
Material and methods
The study includes stomachs of 52 common scoters Melanitta nigra individuals — 32 males (5 immature
ones and 27 adults) and 20 females (11 immature ones and 9 adults). Dead birds were collected in autumn and
winter seasons in the years 1993–2000 in the seaside areas of the western part of the Polish Baltic coast.
Common scoters had died in fishing nets while diving for food. The birds were divided into age categories —
immature birds, under one year of age, and adults, over one year, sexually mature. Four measurements
describing the birds’ body size were established: body
weight BW (exact to 10 g) and three linear measure-
ments: body length, measured from beak to the end of
the rump (with soft tape, exact to 0.5 mm), sternum
length SL (exact to 0.5 mm), tarsus length TL (exact to
1.0 mm) — made according to A. Dziubin and
E. Cooch’s (1992) suggestion. The stomachs’
morphometry included: glandular stomach weight
(GSW) and length (GSL), gizzard weight (GW), length
(GL) and width (GWi). The stomachs were separated
according to differences in the structure of the mucous
membrane lining them. The gizzard’s length was a
fragment between isthmus venticuli and the furthest point
from it; the stomach’s width was the fragment perpen-
dicular to the abovementioned one situated between the
points with the furthest distance between each other
(fig. 1). The linear parameters of both stomachs were
measured exact to 1mm. The stomachs weight was
established exact to 0.01 g after cleaning them from
chyme and drying with filtration tissue. The work also
analyses the value of combined length of both stomachs
(GGL), which was a sum of those two organs’
measurements.
The statistical study of results consisted of
establishing differences between males and females and
between age categories of the birds in absolute average
values of the stomachs measurements and average
values of selected indices of relative size of those
organs using t-Student test. The strength of
interrelationships occurring between the values of
stomachs’ parameters and the values of parameters
describing the birds’ body size and between the
parameters of both stomachs were also examined. For
this reason appropriate Pearson’s linear correlation
coefficients (r) were established.
258 E. Dzia/la-Szczepan´czyk
Fig. 1. Stomach of the Common Scoter Melanitta
nigra (GSL — length of the proventriculus, GL —
length of the gizzard, GWi — breadth of the
gizzard)
Ðèñ. 1. Æåëóäîê ñèíüãè Melanitta nigra (GSL —
äëèíà æåëåçèñòîãî æåëóäêà, GL — äëèíà ìóñ-
êóëüíîãî æåëóäêà, GWi — øèðèíà ìóñêóëüíîãî
æåëóäêà)
G
S
L
G
L
Results
No sexual dimorphism was noticed in the examined group of common scoters in
the size of glandular stomach measurements and gizzard length, despite proved and sta-
tistically confirmed difference in the parameters describing body size between males and
females. The males and females differed significantly in the gizzard width and weight,
and in combined length of both stomachs, where drakes had higher values of those
parameters than ducks (table 1).
The comparative analysis of individuals belonging to the groups of adults and
immature birds within the same sex showed the lack of statistically significant differ-
ences in body measurements and in most of stomachs’ parameters. Only adult individ-
uals in the groups of drakes and ducks had significantly wider gizzards than immature
individuals; and adult females had heavier gizzards than immature individuals of this
sex (table 2).
Dimorphic differences relating to the indices of relative value of selected parame-
ters of the stomachs were only visible in case of combined length of those two organs
related to sternum length, in which females were characterised with higher relative
length of both stomachs than males. In remaining four analysed indices of relative
stomachs’ size no differences were noted between drakes and ducks (table 3).
Gizzard parameters and combined length of both stomachs positively correlated
with at least two, out of four, measurements describing the birds’ body size. A positive
correlation for the relation of GL to BL, TL end SL; GWi to BW end BL; GW to BW
259Morphometric Characteristic of Glandular Stomach and Gizzard…
Ta b l e 1. Differences in absolute body and glandular stomach and gizzard parameters between males and
females of the Common Scoter Melanitta nigra
Òàáëèöà 1. Îòëè÷èÿ àáñîëþòíûõ ïàðàìåòðîâ òåëà, æåëåçèñòîãî è ìóñêóëüíîãî æåëóäêîâ ìåæäó ñàìöàìè
è ñàìêàìè ñèíüãè Melanitta nigra
Measurements
x¯ ± SD
CV
M VS. F
x¯ ± SD
CV
M + F
n = 52
M
n = 32
F
n = 20
No t e. M — males; F — females; x¯ — arithmetic average; SD — standard deviation; CV — coefficient
of variation; t — value of t-Student’s statistics; NS — statistically insignificant differences; p — level of
significance; BW — body weight (g); BL — body length (mm); TL — tarsus length (mm); SL — sternum
length (mm); GSL — absolute length of the glandular stomach (mm); GSW — absolute weight of the
glandular stomach (g); GL — absolute length of the gizzard (mm); GWi — absolute breadth of the gizzard
(mm); GW — absolute weight of the gizzard (g); GGL — absolute length of the glandular stomach and
gizzard (mm).
BW 1345.94±98.99
7.3
1183.0±84.54
7.1
t = 6.10
p < 0.0001
1283.27±122.58
9.5
BL 429.84±11,53
2,7
407±10,69
2,6
t = 7.14
p < 0.0001
421.06±15.79
3.7
TL 45.23±1.23
2.7
43.09±1.3
3.1
t = 5.84
p < 0.0001
44.41±1.65
3.7
SL 100.69±5.61
5.6
93.45±4.51
4.8
t = 4.87
p < 0.0001
97.91±6.27
6.4
GSL 35.49±3.97
11.2
34.26±3.25
9.5
NS 35.02±3.73
10.6
GSW 3.86±0.46
11.9
3.82±0.63
16.5
NS 3.84±0.53
13.7
GL 54.08±3.71
6.9
52.55±1.98
3.8
NS 52.55±1.98
3,8
GWi 56.53±4.01
7.1
51.48±4.64
9.0
t = 4.15
p < 0.0001
54.59±4.90
9.0
GW 48.38±7.72
15.9
41.20±9.1
23.3
t = 2.97
p < 0.001
45.62±9.11
20.0
GGL 89.57±4.96
5.5
86.82±4.15
4.8
t = 2.07
p < 0.05
88.51±4.81
5.4
260 E. Dzia/la-Szczepan´czyk
Ta b l e 2. Differences in absolute body and glandular stomach and gizzard parameters between immature and
adult individuals of the Common Scoter Melanitta nigra
Òàáëèö à 2. Îòëè÷èÿ àáñîëþòíûõ ïàðàìåòðîâ òåëà, æåëåçèñòîãî è ìóñêóëüíîãî æåëóäêîâ ìåæäó
íåçðåëûìè è âçðîñëûìè îñîáÿìè ñèíüãè Melanitta nigra
Measurements
x¯ ± SD
CV
MAdVS. MIm
x¯ ± SD
CV
FAdVS. FImMAd
n = 27
MIm
n = 5
FAd
n = 9
FIm
n = 11
No t e. M — males; F — females; ad — adult individuals; im — immature individuals; — arithmetic
average; SD — standard deviation; CV — coefficient of variation; t — values of t-Student’s statistics; NS —
differences statistically insignificant; p — level of significance. Measurements symbols — see table 1.
BW 1350.7±105.8
7.8
1320±46.37
3.5
NS 1217.8±74.9
6.1
1154.5±84.3
7.3
NS
BL 430.93±12.09
2.8
424±5.5
1.3
NS 407.22±13.02
3.2
406.82±9.02
2.2
NS
TL 45.16±1.32
2.9
45.6±0.49
1.1
NS 43.06±0.93
2,2
43.11±1.68
3,9
NS
SL 100.32±5.92
5.9
102.72±3.14
3.1
NS 94.68±4.26
4.5
92.44±4.65
5,0
NS
GSL 35.50±4,26
12.0
35.44±2.02
5.7
NS 33.44±3.26
9.7
34.93±3,24
9.3
NS
GSW 3.83±0.47
12.3
4.0±0.40
10.1
NS 3.83±0,61
15.9
3.81±0,68
17.7
NS
GL 53.75±3.51
6.53
55.9±4.65
8.3
NS 52.41±2.52
4.8
52.67±1.54
2,9
NS
GWi 57.12±4,03
7.1
53.32±1.96
3.7
t = 2.045
p < 0.05
54.21±4.14
7.6
49.25±3.89
7.9
t = 2.75
p < 0.05
GW 49.41±7.97
16.1
42.81±1.85
4.3
NS 47.32±9.0
19.0
36.19±7.02
19.4
t = 3.109
p < 0.0001
GGL 89.24±5.04
5.6
91.34±4.57
5.0
NS 85.85±5.07
5.9
87.61±3.23
3.7
NS
Ta b l e 3. Comparison of indices of relative values of glandular stomach and gizzard measurements in males and
females of the Common Scoter Melanitta nigra
Òàáëèö à 3. Ñðàâíåíèå èíäåêñîâ îòíîñèòåëüíûõ çíà÷åíèé ïðîìåðîâ æåëåçèñòîãî è ìóñêóëüíîãî
æåëóäêîâ ó ñàìöîâ è ñàìîê ñèíüãè Melanitta nigra
Index
x¯ ± SD CV
M VS. F
x¯ ± SD
CV
M + F
n = 52
M
n = 32
F
n = 20
No t e. M — males; F — females; x̄ — arithmetic mean; SD — standard deviation; CV — coefficient of
variation; t — value of t-Student statistics; NS — non-significant statistical differences; p — significance level.
1 Index of relative organ length (width) — as a relation of organ length (width) to body length
(mm/mm BL) expressed as percentage.
2 Index of relative organ length — as a relation of organ length to tarsus length (mm/mm TL).
3 Index of relative organ length (width) — as a relation of organ length (width) to body weight
(mm/100 g BW).
4 Index of relative organ weight — as a relation of organ weight to body weight (g/g BW) expressed as
percentage.
5 Index of relative organ length — as a relation of an organ length to sternum length (mm/mm SL).
GL/BL1 x 100% 12.58±0.80
6.4
12.92±0.53
4.1
NS 12.71±0.72
5.7
GL/TL2 1.19±0.08
6,3
1.22±0.04
3.8
NS 0.55±0.04
6.7
GWi/BW3 x 100% 4.21±0.36
8.6
4.36±0.41
9.3
NS 4.27±0.38
8.9
GWi/BL1 x 100% 13.16±0.96
7.3
12.65±1.06
8.4
NS 12.69±1.02
7.9
GW/BW4 x100% 3.60±0.55
15.2
3.47±0.71
20.4
NS 3.55±0.61
17.2
GGL/SL5 0.89±0.05
6.1
0.93±0.06
6.6
t = — 2.43
p < 0.05
0.91±0.06
6.6
end BL; GGL to BW, TL end SL were shown. Gizzard length and weight were not in
any relationship with body parameters of the examined group of common scoters
(table 4).
No relationship between parameters of glandular stomach’s length and gizzards
measurements. Glandular stomach weight positively correlated with gizzard width and
its weight. The strongest relationship was noted for the relation of gizzard width and
this organ’s weight (table 4).
Discussion
Common Scoters have well developed both stomachs (fig. 1). The average weight
of empty glandular stomach in the examined group of common scoters was 35 g, and
of empty gizzard — 45.6 g, with the average birds’ body weight of 1283.3 g. In
R. I. Goudie and P. C. Ryan’s studies (1991) conducted on 17 individuals of winter-
ing common scoters, the average gizzard weight reached the value of 42.8 g (with the
average bird’s body weight of 1038 g). The shape and mutual proportions in the size of
both stomachs are related to the kind and amount of food the birds feed on
(Pendergast, Boag, 1973; Paulus, 1982; DuBowy, 1985; Kehoe, Ankney, 1985; White,
Bolen, 1985; Richardson, Wooler, 1986; 1990; Duke, 1997). G. G. Barnes and
V. G. Thomas (1987), examining 18 species belonging to family Anatidae divided into
three trophic group, proved that gizzards of predatory ducks were lighter than stomachs
of omnivorous and herbivorous species. W. P. Kehoe and C. D. Ankney (1985) came
to similar conclusions examining 5 species of ducks from the species Aythya — the
Redhead Aythya americana, feeding on plant food with a lot of indigestible fibre, had
considerably heavier gizzard than remaining species that ate food less burdened with
this ingredient. In relation to predatory ducks from the tribe Mergini, the studies indi-
cate the tendency of the occurrence of heavier gizzards in those species that feed on
bivalves with large shells (Goudie, Rayan, 1991). The Common Scoter is classified as
a species feeding on animal food. Only in summer it eats small amounts of plant food
(del Hoyo et al., 1992). L. Stempniewicz (1986), examining wintering common scot-
ers on the Polish Baltic coast, showed that the birds’ diet consisted mainly of bivalves,
which constituted 93.8% of food mass. Common Scoters Melanitta nigra americana
wintering on the US coast ate mainly bivalves like the Mytilus edulis and Yoldia limat-
ula, which constitute altogether 79.7% of chyme in oesophagus and gizzard
(McGolvrey, 1967). Goude and Ankney (1986), in comparative studies of four winter-
ing duck species from the tribe Mergini, draw attention to small diversity of common
scoters’ food comparing to other species — the Coomon Blue Mussel Mytilus edulis
constituted 98% of wet food mass in those birds’ oesophagus. Moreover, common scot-
ers were characterised by relatively short time of feeding comparing to other species
261Morphometric Characteristic of Glandular Stomach and Gizzard…
Ta b l e 4. Coefficients of correlation for interdependent among measurement of glandular stomach and gizzard
and parameters of body in the Common Scoter Melanitta nigra (parameter symbols see table 1)
Ò à á ëèö à 4. Êîýôôèöèåíòû êîððåëÿöèè äëÿ âçàèìîçàâèñèìûõ ïðîìåðîâ æåëåçèñòîãî è ìóñêóëüíîãî
æåëóäêîâ è ïàðàìåòðîâ òåëà ñèíüãè Melanitta nigra (óñëîâíûå îáîçíà÷åíèÿ ïàðàìåòðîâ ñì. òàáë. 1)
BW BL TL SL GSW GL GWi GW GGL
* Siglificant at < 0.05.
** Siglificant at < 0.01.
*** Siglificant at < 0.001.
NS — non-siglificant.
GSL NS NS NS NS NS NS NS NS 0.74***
GSW NS NS NS NS – NS 0.33* 0.39** NS
GL NS 0.40** 0.43** 0.42** – NS NS 0.63***
GWi 0.54*** 0.48*** NS NS – 0.87*** NS
GW 0.51*** 0.44*** NS NS – NS
GGL 0.29* NS 0.35** 0.41** –
from the tribe Mergini (Goudze, Ankney, 1986). The examined common scoters were
collected in winter months, in the period when the birds feed only on animal food,
which probably influenced the value of both stomachs’ parameters.
The coefficient of variability for some morphometric features of stomachs in the
examined group of common scoters reached quite high values and could be a result of
morphological and anatomical variability of birds collected during seven years in vari-
ous winter months (from October to March). The variability of the structure of diges-
tive organs within a species may have various grounds. Birds’ stomach is a dynamic
organ and is subject to continuous morphological changes in time (Kehoe et al., 1988;
Strack, 1999; Barboza, Jorde, 2002). Many researchers point out that changes regis-
tered in alimentary tract in omnivorous and herbivorous birds especially become visible
in the gizzard as a result of changing food containing fibre (Moss, 1972; Burton et al.,
1979; Whyte, Bolen, 1985). M. W. Tome (1984) draw attention to changes taking place
in gizzard weight of females of the Ruddy Duck Oxyura jamaicensis in the nesting peri-
od as a result of qualitative changes of food taken at that time by the birds. The amount
of eaten food can also significantly influence the birds’ digestive system (Sabvory,
Gentile, 1976; Ankney, 1977; Raveling, 1979; Drobney, 1984; Ankney, Scott, 1988).
In the examined group of common scoters the lack of sexual dimorphism was
noticed in the average values of glandular stomach and gizzard length, despite clear dif-
ference in the body size between males and females. Clear differences between drakes
and ducks were visible in relation to gizzard width and weight, as well as both stom-
achs length. Differences, or their lack, in respect to the parameters describing the size
of stomachs between males and females of common scoters may have various reasons.
A lot of authors point out to periodical or permanent variability of males’ and females’
diet of many bird species, and consequently a morphological variability of their diges-
tive organs. S.-A. Bengston (1971), comparing the food of females and males of six rep-
resentatives of sub-family Anatinae showed significant differences in food preferences
between sexes of individual species. In this author’s (Bengston, 1971) research, main-
ly larvae of Chiromonidae were found in common scoter females’ oesophagus, which
constituted 64% of wet chyme of this organ. On the other hand, chyme in oesophagus
of this species’ males consisted mainly of fish eggs (86% of wet food mass of the
oesophagus). In research carried out on the wintering Tufted Duck Aythya fuligula, dif-
ferences in food preferences between females and males of this species also concerned
the mussels’ size — drakes ate mussels Corbicula japonia with bigger shells than ducks
did (Oka et al., 1999). C. D. Ankney and A. D. Afton (1988) pointed out at differ-
ences in the percentage of individual food components and differences in gizzard weight
between males and females of Northern Shoveler Anas clypeata in the nesting period.
The analysis of dimorphic differences connected with sex in respect to the indices
of relative stomach size of the examined group of common scoters showed that females
reached higher values of relative length of both stomachs (calculated in relation to ster-
num length) than males. However, in respect to other parameters of relative stomachs’
size related to remaining body measurements, no differences between drakes and ducks
were found. Perhaps sternum length and both stomachs length — parameters close to
the value of the coefficient of variability in the groups of males and females, better char-
acterise dimorphic differences. Supposedly, the differences relating to digestive organs
size between males and females may also have genetic background. M. R. Miller’s
(1974) experiment carried out on wild mallards kept in captivity showed that smaller
females had longer intestines than bigger males, despite the fact that they were fed on
the same forage. The author (Miller, 1974) suggests that the Mallard’s females (Anas
platyrhynchos) have genetically conditioned better ability to adapt their morphology of
digestive organs to changes of diet that males of this species have. C. D. Ankney (1997),
examining males and females of the Lesser Snow Geese Chen caerulescens caerulescens
262 E. Dzia/la-Szczepan´czyk
in the nesting period, attributes differences in changes occurring in gizzard weight in
both sexes both to the influence of the changing diet and inborn features of this species.
The lack of dimorphism connected with age in respect to most stomach parame-
ters in the examined group of common scoters may be attributed to unequal participa-
tion of adult and immature birds. It may also be a result of the lack of differences in
body size between the birds’ age groups. Also no significant difference was proven in
gizzard weight between immature and adult individuals of the Black Duck Anas rubripes
not differing in body size (Reinecke et al., 1982). But in respect to jejunum and ileum
of wintering immature and adult common scoters that did not differ in body size, it was
shown that the individuals from the group of immature birds had this organ longer than
adult individuals (Dzia/la-Szczepan´czyk, 2004). R. J. Whyte and E. G. Bolen (1985)
showed differences in gizzard weight both between males and females as well as between
age groups of adult and juvenile birds in mallards Anas platyrhynchos examined in the
period from autumn to early spring — but statistical significance of those differences
was not studied.
In the examined group of common scoters no relationship of glandular stomach
with the birds’ body measurements were noticed. Gizzard parameters, however, posi-
tively correlated with at less two measurements describing common scoters’ body size.
Presumably, both stomachs react differently to the change of diet, which is reflected,
among others, in the relationship of those organs’ parameters with the birds’ body mea-
surements. Perhaps common scoters’ glandular stomach is subject to faster morpholog-
ical modifications under the influence of food changes than the gizzard, and changes
taking place in it are not parallel to the changes in the birds’ body build. In interspe-
cific comparisons performed on 19 representatives of waders Charadrii it was shown
that both stomachs’ weight positively correlated with this group of birds’ body weight
(Piersma et al., 1993). In K. C. Richardson and R. D. Wooler’s (1986) studies, how-
ever, gizzard weight of six species of Passeriformes feeding on honey did not come into
any relationship with those birds’ body weight. Perhaps the obtained results were asso-
ciated with the diet of the compared group species. It the group of Charadrii, there are
herbivorous and omnivorous species, feeding on low-calory food containing indigestible
fibre. The food of the studied of Passeriformes (honey) is more easily assimilated.
The lack of the relationship of glandular stomach length with gizzard’s parameters
may also indicate a different reaction of both organs to the diet changing in time. The
dynamics of morphological changes taking place in glandular stomach under the influ-
ence of food may be similar to the reaction of the intestine. This organ in water birds
adapts so fast to the changing died that its size may be used as a good indicator of food
preferences of this group of birds (Miller, 1974, 1975). As many experiments prove, giz-
zard may react differently to the change of food than other parts of the digestive sys-
tem. An experiment performed on the Mallard Anas platyrhynchos kept in captivity
proved considerable differences in gizzard’s reactions to higher dose of fibre in the diet
comparing to the intestine — gizzard weight, after initial rise, dramatically decreased
after fifteen days of the experiment, whereas intestine length had a rising tendency
(Kehoe et al., 1988). S. A. Halse (1984, 1985) noticed a considerable increase of giz-
zard weight in the moulting period of Spur Winged Goose Plectropterus gambensis and
Egyptian Goose Alopochen aegyptiacus. The author (Halse, 1984, 1985) suggests that the
increase of weight of this organ may have been influenced, apart from the change of
food in that period, also by another factor because the changes in gizzard were bigger
than in other parts of the digestive system in both species.
Conclusions
Sexual dimorphism was only evident in three parameters: gizzard width and weight
and both stomachs’ length — drakes had significantly higher values than ducks. In most
parameters of stomachs related to body measurements, no significant differences
263Morphometric Characteristic of Glandular Stomach and Gizzard…
between females and males were noticed; only the index of relative length of both stom-
achs related to sternum length occurred to be higher in ducks than in drakes.
No significant differences were found between adult and immature birds in body
weight and the value of most stomachs’ parameters. A positive correlation for the rela-
tion of GL to BL, TL, SL; GWi to BW, BL; GW to BW, BL; GGL to BW, TL, SL
were shown.
Apart from glandular stomach length and weight, other stomachs’ parameters pos-
itively correlated with at least two parameters describing the birds’ body size.
No relationship between glandular stomach length and gizzard parameters was found.
Glandular stomach weight was in the positive correlation with gizzard width and weight.
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265Morphometric Characteristic of Glandular Stomach and Gizzard…
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