Bird measurement: Difference between revisions
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{{Short description|Bird biometrics}} |
{{Short description|Bird biometrics}} |
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[[File:BirdMorphometrics.jpg|thumb|Most measurement requires the use of [[calipers]]. Here the measurement of length, wing, tail, tarsus and two forms of culmen measurement are shown.]] |
[[File:BirdMorphometrics.jpg|thumb|Most measurement requires the use of [[calipers]]. Here the measurement of length, wing, tail, tarsus and two forms of culmen measurement are shown.]] |
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'''Bird measurement''' or '''bird biometrics''' are approaches to quantify the [[size]] of [[bird]]s in scientific studies. The |
'''Bird measurement''' or '''bird biometrics''' are approaches to quantify the [[size]] of [[bird]]s in scientific studies. The variation in dimensions and [[weight]]s across birds is one of the fundamental sources of diversity among birds, and even Within species, dimensions may vary across populations [[Intraspecific variability|within species]], between the sexes and depending on [[Biomarkers of aging|age]] and condition. In order for measurements to be useful, they need to be well defined so that measurements taken are consistent and comparable with those taken by others or at other points of time. Measurements can be useful to identify species, quantify functional and [[ecomorphology|ecomorphological]] differences, study growth, variation between geographically separated forms, identify [[Sexual dimorphism measures|differences between the sexes]], age or otherwise characterize individuals birds. While certain measurements are regularly taken in the field to study living birds some others are applicable only to specimens in [[bird collections]] or measurable only in the laboratory. The conventions used for measurement can vary between authors and works, making comparisons of sizes a matter that needs considerable care.<ref>{{cite journal |title=Measurements of birds|last1=Baldwin| first1=S. Prentiss| first2=Harry C.| last2=Oberholser |first3=Leonard G.| last3=Worley | year=1931 | journal=Scientific Publications of the Cleveland Museum of Natural History| volume=2 |pages=[https://archive.org/details/measurementsofbi00bald/page/n22 1]–165 |url=https://archive.org/details/measurementsofbi00bald}}</ref> |
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==Methods and considerations== |
==Methods and considerations== |
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All measurement is prone to [[observational error|error]], both systematic and random. The measurement of certain bird characteristics can further [[measurement uncertainty|vary]] greatly depending on the method used. The total length of a bird is sometimes measured by putting a dead bird on its back and gently pressing the head so that the bill point to the tail tip can be measured. This can however vary with the |
All measurement is prone to [[observational error|error]], both systematic and random. The measurement of certain bird characteristics can further [[measurement uncertainty|vary]] greatly depending on the method used. The total length of a bird is sometimes measured by putting a dead bird on its back and gently pressing the head so that the bill point to the tail tip can be measured. This can however vary with the degree of stretching of the neck and cannot be measured in preserved skins in [[bird collections]]. The wing length usually defined as the distance between the [[carpometacarpal joint]] and the longest primary can vary depending on whether the natural curvature of the wing is preserved or the measurement is taken on a flattened wing. The measurement can additionally vary depending on whether a [[tape measure|flexible tape]] measure is used over the curve or if measured with a rigid ruler. The definition of the length of the tail can vary when some of them have elongations, forking or other modifications.<ref>{{cite journal|author=Morgan J.H. |year=2004| title=Remarks on the taking and recording of biometric measurements in bird ringing |journal=Ring|volume=26|issue=1|pages=71–78 |url=http://thering.ug.edu.pl/pdf/26-1/morgan.pdf |doi=10.2478/v10050-008-0058-2}}</ref><ref name="Goodenough AE; Stafford R; Catlin-Groves CL; Smith AL & Hart AG 2010 323–334">{{cite journal|author1=Goodenough AE |author2=Stafford R |author3=Catlin-Groves CL |author4=Smith AL |author5=Hart AG |name-list-style=amp |year=2010|title=Within- and among-observer variation in measurements of animal biometrics and their influence on accurate quantification of common biometric-based condition indices|journal=Ann. Zool. Fennici|volume=47| pages=323–334|url=http://www.sekj.org/PDF/anz47-free/anz47-323.pdf|doi=10.5735/086.047.0503}}</ref> The weights of birds are even more prone to variability with their feeding and health condition and in the case of [[Bird migration|migratory species]] differ quite widely across seasons even for a single individual. |
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Despite the variations, measurements are routinely taken in the process of [[bird ringing]] |
Despite the variations, measurements are routinely taken in [[taxonomy|taxonomic]] studies and in the process of [[bird ringing]]. Several of the measurements are considered quite reliable and well defined, at least in the vast majority of birds. Although field measurements are usually [[univariate]], laboratory techniques can often make use of multivariate measurements derived from an [[Multivariate statistics|analysis of variation]] and correlations of these univariate measures. These can often indicate variations more reliably.<ref name="Bergtold, WH 1925 59–61">{{cite journal|url=http://sora.unm.edu/sites/default/files/journals/condor/v027n02/p0059-p0061.pdf |title=The Relative Value of Bird Measurements|author=Bergtold, WH|year=1925| pages=59–61| volume=27| issue=2| doi=10.2307/1363054| journal=The Condor}}</ref><ref name="Rising, JD & KM Somers 666–674">{{cite journal|url=http://sora.unm.edu/sites/default/files/journals/auk/v106n04/p0666-p0674.pdf |title=The measurement of overall body size in birds|author1=Rising, JD |author2=KM Somers |name-list-style=amp |journal=The Auk|volume=106| issue=4|pages=666–674}}</ref><ref>{{cite journal| title=Measurement Error of External and skeletal variables in birds and its effect on principal components|vauthors=Lougheed SC, Arnold TW, Bailey RC |url=http://sora.unm.edu/sites/default/files/journals/auk/v108n02/p0432-p0436.pdf |journal=The Auk |volume=108| issue=2| pages=432–436| year=1991}}</ref> |
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==Total Body Length== |
==Total Body Length== |
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[[File:Pustelga lep.jpg|thumb|Measuring a [[common kestrel]] electrocuted on a power line]] |
[[File:Pustelga lep.jpg|thumb|Measuring a [[common kestrel]] electrocuted on a power line]] |
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The total length of the body (also bill-to-tail length) of a bird is usually measured from dead specimens prior to their being skinned for preservation. The measurement is made by laying the bird on its back |
The total length of the body (also bill-to-tail length) of a bird is usually measured from dead specimens prior to their being skinned for preservation. The measurement is made by laying the bird on its back, stretching out the neck, making the beak to point forward and measuring between the tip of the bill and the tip of the tail. This measurement is however prone to error and is rarely ever used for any comparative or other scientific study.<ref name=pcr/> |
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==Culmen== |
==Culmen== |
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[[File:MeasureBeakThrush.jpg|thumb|Measuring the culmen]] |
[[File:MeasureBeakThrush.jpg|thumb|Measuring the culmen]] |
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The upper margin of the beak or bill is referred to as the culmen and the measurement is taken using calipers with one jaw at the tip of the upper mandible and the other at base of the skull or the |
The upper margin of the beak or bill is referred to as the culmen and the measurement is taken using calipers with one jaw at the tip of the upper mandible and the other at base of the bill (at the junction with the skull, a measurement called "total culmen") or where the feathers conceal the culmen (a measurement called "exposed culmen"). In the case of birds of prey where the tip of the mandible may form a long festoon, the length of the festoon may be measured separately as well. In birds of prey the measurement is usually from the bill tip to the ceres. In some birds the distance between the back of the skull and the tip of the beak may be more suitable and less prone to variation resulting from the difficulty of interpreting the feathered base of the mandible.<ref>{{cite journal|volume=71| issue=4| pages=606–611| title=What do different bill measures measure and what is the best method to use in granivorous birds?|vauthors=Borras A, Pascual J, Senar JC |journal=J. Field Ornithol.|url=http://www.bcn.es/museuciencies_fitxers/imatges/FitxerContingut1987.pdf}}</ref> |
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==Head== |
==Head== |
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Revision as of 13:58, 14 September 2023
Bird measurement or bird biometrics are approaches to quantify the size of birds in scientific studies. The variation in dimensions and weights across birds is one of the fundamental sources of diversity among birds, and even Within species, dimensions may vary across populations within species, between the sexes and depending on age and condition. In order for measurements to be useful, they need to be well defined so that measurements taken are consistent and comparable with those taken by others or at other points of time. Measurements can be useful to identify species, quantify functional and ecomorphological differences, study growth, variation between geographically separated forms, identify differences between the sexes, age or otherwise characterize individuals birds. While certain measurements are regularly taken in the field to study living birds some others are applicable only to specimens in bird collections or measurable only in the laboratory. The conventions used for measurement can vary between authors and works, making comparisons of sizes a matter that needs considerable care.[1]
Methods and considerations
All measurement is prone to error, both systematic and random. The measurement of certain bird characteristics can further vary greatly depending on the method used. The total length of a bird is sometimes measured by putting a dead bird on its back and gently pressing the head so that the bill point to the tail tip can be measured. This can however vary with the degree of stretching of the neck and cannot be measured in preserved skins in bird collections. The wing length usually defined as the distance between the carpometacarpal joint and the longest primary can vary depending on whether the natural curvature of the wing is preserved or the measurement is taken on a flattened wing. The measurement can additionally vary depending on whether a flexible tape measure is used over the curve or if measured with a rigid ruler. The definition of the length of the tail can vary when some of them have elongations, forking or other modifications.[2][3] The weights of birds are even more prone to variability with their feeding and health condition and in the case of migratory species differ quite widely across seasons even for a single individual.
Despite the variations, measurements are routinely taken in taxonomic studies and in the process of bird ringing. Several of the measurements are considered quite reliable and well defined, at least in the vast majority of birds. Although field measurements are usually univariate, laboratory techniques can often make use of multivariate measurements derived from an analysis of variation and correlations of these univariate measures. These can often indicate variations more reliably.[4][5][6]
Total Body Length
The total length of the body (also bill-to-tail length) of a bird is usually measured from dead specimens prior to their being skinned for preservation. The measurement is made by laying the bird on its back, stretching out the neck, making the beak to point forward and measuring between the tip of the bill and the tip of the tail. This measurement is however prone to error and is rarely ever used for any comparative or other scientific study.[7]
Culmen
The upper margin of the beak or bill is referred to as the culmen and the measurement is taken using calipers with one jaw at the tip of the upper mandible and the other at base of the bill (at the junction with the skull, a measurement called "total culmen") or where the feathers conceal the culmen (a measurement called "exposed culmen"). In the case of birds of prey where the tip of the mandible may form a long festoon, the length of the festoon may be measured separately as well. In birds of prey the measurement is usually from the bill tip to the ceres. In some birds the distance between the back of the skull and the tip of the beak may be more suitable and less prone to variation resulting from the difficulty of interpreting the feathered base of the mandible.[8]
Head
In some cases it is more reliable to measure the distance between the back of the skull and the tip of the bill. This measure is then termed as the head. This measurement is however not suitable for use with living birds that have strong neck musculature such as the cormorants.[7]
Tarsus
The shank of the bird is usually exposed and the length from the inner bend of the tibiotarsal articulation to the base of the toes which is often marked by a difference in the scalation is used as a standard measure. In most cases the tarsus is held bent but in some cases the measurement may be made of the length of this bone as visible on the outer side of the bend to the base of the toes.
Foot
In the case of cranes and bustards, the length of the tarsus is often measured along with the length of the longest toe to the tip of the claw.[7]
Tail
The measurement of the tail is taken from the base of the tail to the tip of the longest feathers. In the case where special structures such as racquets or streamers exist, these are separately measured. In some cases the difference between the longest and shortest feathers, that is the depth of the fork or notch can also be of use.
Wing
The wing is usually measured from the carpal joint (the bend of the wing) to the tip of the longest primary feathers. Often the wings and feathers may be flattened so that the measure is maximized but in some cases the chord length with natural curvature is preferred.[4][5] In some cases the relative lengths of the longest primaries and the pattern of size variation among them can be important to measure. The wing width can also be measured from the carpal joint to the tip of the first secondary feather.[9]
Wingspan
The wingspan is the distance between wingtips when the wings are held outstretched. This measurement is particularly prone to variation resulting from wing posture and is rarely used except as a rough indicator of size, but it is an important measurement for studies of bird flight.[9] Additionally, this cannot be easily and reliably measured in the field with live birds.
Wing Area
The area of a single wing can be measured manually by tracing the outline of the wing on grid paper and counting grids and fractions.[10] Alternatively, it can be obtained digitally using a photograph of the spread wing including a ruler scale and then using software such as ImageJ.[9] In bird flight aerodynamics, the area of interest is the total wing area, that is, the area of both wings plus the area of the intervening portion of the body.[10] The total wing area can also be estimated using linear measurements of the length and width of the hand-wing, and the wingspan.[11]
Weight
The total body weight is an important biological measurement, usually used as a proxy for body mass. However, due to its variability with seasons and body condition, it is not recommended to be used as an indicator of body size. It is however useful in quantifying growth in laboratory conditions and for use in clinical diagnostics as an indicator of physiological conditions, and it is a fundamental quantity in bird aerodynamics.[9] Birds in captivity are often heavier than wild specimens. Migratory birds gain weight prior to the migratory period but lose weight during handling or temporary captivity. Dead birds tend to weigh less than in life. Even during the course of a day, the weight can vary by 5 to 10%. The male emperor penguin loses 40% of its weight during the course of incubation.[12]
References
- ^ Baldwin, S. Prentiss; Oberholser, Harry C.; Worley, Leonard G. (1931). "Measurements of birds". Scientific Publications of the Cleveland Museum of Natural History. 2: 1–165.
- ^ Morgan J.H. (2004). "Remarks on the taking and recording of biometric measurements in bird ringing" (PDF). Ring. 26 (1): 71–78. doi:10.2478/v10050-008-0058-2.
- ^ Goodenough AE; Stafford R; Catlin-Groves CL; Smith AL & Hart AG (2010). "Within- and among-observer variation in measurements of animal biometrics and their influence on accurate quantification of common biometric-based condition indices" (PDF). Ann. Zool. Fennici. 47: 323–334. doi:10.5735/086.047.0503.
- ^ a b Bergtold, WH (1925). "The Relative Value of Bird Measurements" (PDF). The Condor. 27 (2): 59–61. doi:10.2307/1363054.
- ^ a b Rising, JD & KM Somers. "The measurement of overall body size in birds" (PDF). The Auk. 106 (4): 666–674.
- ^ Lougheed SC, Arnold TW, Bailey RC (1991). "Measurement Error of External and skeletal variables in birds and its effect on principal components" (PDF). The Auk. 108 (2): 432–436.
- ^ a b c Rasmussen PC, Anderton JC (2005). Birds of South Asia. The Ripley Guide. Volume 2. Washington DC & Barcelona: Smithsonian Institution & Lynx Edicions. pp. 18–19.
- ^ Borras A, Pascual J, Senar JC. "What do different bill measures measure and what is the best method to use in granivorous birds?" (PDF). J. Field Ornithol. 71 (4): 606–611.
- ^ a b c d Claramunt, S.; Wright, N. A. (2017). "Using museum specimens to study flight and dispersal.". In Webster, M. S. (ed.). Emerging Frontiers in Collections-based Ornithological research: the Extended Specimen. Studies in Avian Biology 50. CRC Press. pp. 127–141. ISBN 9781315120454.
- ^ a b Pennycuick, Colin J (2008). "Modelling the Flying Bird". Theoretical Ecology Series. doi:10.1016/s1875-306x(08)x0002-4. ISSN 1875-306X.
- ^ Fu, HY; Su, M; Chu, JJ; Margaritescu, A; Claramunt, S (2023). "New methods for estimating the total wing area of birds". Ecology and Evolution. 13 (9). doi:10.1002/ece3.10480.
- ^ George A. Clark, Jr. (1979). "Body Weights of Birds: A Review" (PDF). The Condor. 81 (2): 193–202. doi:10.2307/1367288.
External links
- Bird Handling and Ringing Techniques including biometric measurements
- SAFRING (South Africa Bird Ringing Unit) Bird Ringing manual