Morphometric indices of body condition in birds: A review

Journal of Ornithology

Volumn 153, Issue 1, 2012, Pages 1-22

  Labocha, Marta K ^a,b   Hayes, Jack P ^a  

^a UNIVERSITY OF NEVADA   (United States)

^b RICE UNIVERSITY   (United States)

Author keywords

Birds; Body composition; Body size; Condition index; Energy reserves

Indexed keywords

BIRD; BODY CONDITION; BODY MASS; MORPHOMETRY; MULTIPLE REGRESSION; ORNITHOLOGY;

AVES;

EID: 84855323653     PISSN: 21937192     EISSN: 21937206     Source Type: Journal    
DOI: 10.1007/s10336-011-0706-1     Document Type: Review

References (146)

1. Allison DB, Paultre F, Goran MI, Poehlman ET, Heymsfield SB (1995) Statistical considerations regarding the use of ratios to adjust data. Int J Obes 19: 644-652.
2. Ankney CD, Afton AD (1988) Bioenergetics of breeding northern shovelers: diet, nutrient reserves, clutch size, and incubation. Condor 90: 459-472.
3. Ankney RD, Alisauskas RT (1991) Nutrient-reserve dynamics and diet of breeding female gadwalls. Condor 93: 799-810.
4. Anteau MJ, Afton AD (2008) Using plasma-lipid metabolites to index changes in lipid reserves of free-living lesser scaup (Aythya affinis). Auk 125: 354-357.
5. Ardia DR (2005) Super size me: an experimental test of the factors affecting lipid content and the ability of residual body mass to predict lipid stores in nestling European starlings. Funct Ecol 19: 414-420.
6. Bachman G, Widemo F (1999) Relationships between body composition, body size and alternative reproductive tactics in a lekking sandpiper, the ruff (Philomachus pugnax). Funct Ecol 13: 411-416.
7. Bailey RO (1979) Methods of estimating total lipid-content in the redhead duck (Aythya Americana) and an evaluation of condition indexes. Can J Zool 57: 1830-1833.
8. Barthelmess EL, Phillips ML, Schuckers ME (2006) The value of bioelectrical impedance analysis vs. condition indices in predicting body fat stores in North American porcupines (Erethizon dorsatum). Can J Zool 84: 1712-1720.
9. Barzen JA, Serie JR (1990) Nutrient reserve dynamics of breeding canvasbacks. Auk 107: 75-85.
10. Battley PF, Piersma T, Dietz MW, Tang SX, Dekinga A, Hulsman K (2000) Empirical evidence for differential organ reductions during trans-oceanic bird flight. Proc R Soc Lond B 267: 191-195.
11. Battley PF, Piersma T, Rogers DI, Dekinga A, Spaans B, van Gils JA (2004) Do body condition and plumage during fuelling predict northwards departure dates of great knots Calidris tenuirostris from north-west Australia? Ibis 146: 46-60.
12. Bech C, Ostnes JE (1999) Influence of body composition on the metabolic rate of nestling European shags (Phalacrocorax aristotelis). J Comp Physiol B 169: 263-270.
13. Bergan JF, Smith LM (1993) Survival rates of female mallards wintering in the Playa Lakes region. J Wildl Manag 57: 570-577.
14. Bergstrom BJ, Sherry TW (2008) Estimating lipid and lean body mass in small passerine birds using TOBEC, external morphology and subcutaneous fat-scoring. J Avian Biol 39: 507-513.
15. Blanchard BD (1941) The white-crowned sparrows (Zonotrichia leucophrys) of the Pacific seaboard: environment and annual cycle. Univ Calif Publ Zool 46: 1-180.
16. Bleeker M, Kingma SA, Szentirmai I, Szekely T, Komdeur J (2005) Body condition and clutch desertion in penduline tit Remiz pendulinus. Behaviour 142: 1465-1478.
17. Blem CR (1981) Geographic variation in mid-winter body composition of starlings. Condor 83: 370-376.
18. Blem CR (1984) Ratios in avian physiology. Auk 101: 153-155.
19. Blem CR (1990) Avian energy stores. In: Johnston RF (ed) Current ornithology, vol 7. Plenums, New York, pp 59-114.
20. Blem CR, Shelor MH (1986) Multiple-regression analyses of midwinter fattening of the white-throated sparrow. Can J Zool 64: 2405-2411.
21. Blums P, Clark RG, Mednis A (2002) Patterns of reproductive effort and success in birds: path analyses of long-term data from European ducks. J Anim Ecol 71: 280-295.
22. Blums P, Nichols JD, Hines JE, Lindberg MS, Mednis A (2005) Individual quality, survival variation and patterns of phenotypic selection on body condition and timing of nesting in birds. Oecologia 143: 365-376.
23. Boos M, Zorn T, Koch A, Le Maho Y, Robin JP (2000) Determining body fuels of wintering mallards. CR Acad Sci Life Sci 323: 183-193.
24. Boos M, Zorn T, Le Maho Y, Groscolas R, Robin JP (2002) Sex differences in body composition of wintering mallards (Anas platyrhynchos): possible implications for survival and reproductive performance. Bird Study 49: 212-218.
25. Bowler JM (1994) The condition of Bewick's swans Cygnus columbianus bewickii in winter as assessed by their abdominal profiles. Ardea 82: 241-248.
26. Briggs SV (1989) Morphological prediction of body condition in maned ducks. Aust Wildl Res 16: 605-609.
27. Bromley RG, Jarvis RL (1993) The energetics of migration and reproduction of dusky Canada geese. Condor 95: 193-210.
28. Brown ME (1996) Assessing body condition in birds. Curr Ornithol 13: 67-135.
29. Burton NHK, Rehfisch MM, Clark NA, Dodd SG (2006) Impacts of sudden winter habitat loss on the body condition and survival of redshank Tringa totanus. J Appl Ecol 43: 464-473.
30. Bustnes JO, Erikstad KE, Bjorn TH (2002) Body condition and brood abandonment in common eiders breeding in the high Arctic. Waterbirds 25: 63-66.
31. Calder WA III (1984) Size, function, and life history. Harvard University Press, Cambridge.
32. Carpenter FL, Hixon MA, Beuchat CA, Robert W, Russell RW, Paton DC (1993) Biphasic mass gain in migrant hummingbirds: body composition changes, torpor, and ecological significance. Ecology 74: 1173-1182.
33. Castro G, Myers JP (1990) Validity of predictive equations for total-body fat in sanderlings from different nonbreeding areas. Condor 92: 205-209.
34. Chan K (1995) Comparative study of winter body composition of resident and migrant grey-breasted silvereyes. Auk 112: 421-428.
35. Chappell WA, Titman RD (1983) Estimating reserve lipids in greater scaup (Aythya marila) and lesser scaup (A. affinis). Can J Zool 61: 35-38.
36. Christe P, Moller AP, de Lope F (1998) Immunocompetence and nestling survival in the house martin: the tasty chick hypothesis. Oikos 83: 175-179.
37. Christians JK (2000) Producing extra eggs does not deplete macronutrient reserves in European starlings Sturnus vulgaris. J Avian Biol 31: 312-318.
38. Conway CJ, Eddleman WR, Simpson KL (1994) Evaluation of lipid indexes of the wood-thrush. Condor 96: 783-790.
39. Costantini D, Casagrande S, Dell'Omo G (2007) MF magnitude does not affect body condition, pro-oxidants and anti-oxidants in Eurasian kestrel (Falco tinnunculus) nestlings. Environ Res 104: 361-366.
40. Cox RR, Afton AD (1998) Effects of capture and handling on survival of female northern pintails. J Field Ornithol 69: 276-287.
41. Daan S, Masman D, Groenewold A (1990) Avian basal metabolic rates: their association with body composition and energy expenditure in nature. Am J Physiol 259: R333-R340.
42. Darlington RB, Smulders TV (2001) Problems with residual analysis. Animal Behav 62: 599-602.
43. DeLong JP, Gessaman JA (2001) A comparison of noninvasive techniques for estimating total body fat in sharp-shinned and Cooper's hawks. J Field Ornithol 72: 349-364.
44. DeVault TL, Rhodes OE, Smith LM (2003) Condition indices for wintering American wigeon. Wildl Soc Bull 31: 1132-1137.
45. Dinsmore SJ, Collazo JA (2003) The influence of body condition on local apparent survival of spring migrant sanderlings in coastal North Carolina. Condor 105: 465-473.
46. Dombrowski P, Bourgeois JC, Couture R, Linard C (2003) Estimation of carcass fat and protein in northern pintails (Anas acuta) during spring migration. J Wildl Dis 39: 620-626.
47. Donnelly RE, Sullivan KA (1998) Foraging proficiency and body condition of juvenile American dippers. Condor 100: 385-388.
48. Dufour KW, Weatherhead PJ (1991) A test of the condition-bias hypothesis using brown-headed cowbirds trapped during the breeding-season. Can J Zool 69: 2686-2692.
49. Eichhorn G, Visser HK (2008) Evaluation of the deuterium dilution method to estimate body composition in the barnacle goose: accuracy and minimum equilibration time. Physiol Biochem Zool 81: 508-518.
50. Evans RM, McMahon BF (1987) Within-brood variation in growth and condition in relation to brood reduction in the American white pelican. Wilson Bull 99: 190-201.
51. Feret M, Bety J, Gauthier G, Giroux JF, Picard G (2005) Are abdominal profiles useful to assess body condition of spring staging greater snow geese? Condor 107: 694-702.
52. Freckleton RP (2002) On the misuse of residuals in ecology: regression of residuals vs. multiple regression. J Anim Ecol 71: 542-545.
53. Fuller WA (1987) Measurement error models. Wiley, New York.
54. Garcia-Berthou E (2001) On the misuse of residuals in ecology: testing regression residuals vs. the analysis of covariance. J Anim Ecol 70: 708-711.
55. Gauthier G, Bedard J (1985) Fat reserves and condition indexes in greater snow geese. Can J Zool 63: 331-333.
56. Golet GH, Irons DB (1999) Raising young reduces body condition and fat stores in black-legged kittiwakes. Oecologia 120: 530-538.
57. Green AJ (2001) Mass/length residuals: measures of body condition or generators of spurious results? Ecology 82: 1473-1483.
58. Groscolas R, Schreiber L, Morin F (1991) The use of tritiated-water to determine protein and lipid utilization in fasting birds-a validation-study in incubating great-winged petrels, Pterodroma macroptera. Physiol Zool 64: 1217-1233.
59. Hayes JP, Shonkwiler JS (2001) Morphometric indicators of body condition: worthwhile or wishful thinking? In: Spearman JR (ed) Body composition analysis of animals: a handbook of non-destructive methods. Cambridge University Press, Cambridge, pp 8-38.
60. Helms CW, Drury WH Jr (1960) Winter and migratory weight and fat field studies on some North American buntings. Bird Banding 31: 1-40.
61. Helms CW, Aussiker WH, Bower EB, Fretwell SD (1967) A biometric study of major body components of the slate-colored junco, Junco hyemalis. Condor 69: 560-578.
62. Hohman WL (1993) Body-composition of wintering canvasbacks in Louisiana-dominance and survival implications. Condor 95: 377-387.
63. Hohman WL, Taylor TS (1986) Indices of fat and protein for ring-necked ducks. J Wildl Manag 50: 209-211.
64. Iverson GC, Vohs PA (1982) Estimating lipid-content of sandhill cranes from anatomical measurements. J Wildl Manag 46: 478-483.
65. Jakob EM, Marshall SD, Uetz GW (1996) Estimating fitness: a comparison of body condition indices. Oikos 77: 61-67.
66. Jamieson SE, Gilchrist HG, Merkel FR, Falk K, Diamond AW (2006) An evaluation of methods used to estimate carcass composition of common eiders Somateria mollissima. Wildl Biol 12: 219-226.
67. Jasienski M, Bazzaz FA (1999) The fallacy of ratios and the testability of models in biology. Oikos 84: 321-326.
68. Jehl JR Jr (1997) Cyclical changes in body composition in the annual cycle and migration in the eared grebe Podiceps nigricollis. J Avian Biol 28: 132-142.
69. Jenni L, Jenni-Eierman S (1987) Body weight and energy reserves of bramblings in winter. Ardea 75: 271-284.
70. Jenni L, Jenni-Eiermann S, Spina F, Schwabl H (2000) Regulation of protein breakdown and adrenocortical response to stress in birds during migratory flight. Am J Physiol 278: R1182-R1189.
71. Johnson DH, Krapu GL, Reinecke KJ, Jorde DG (1985) An evaluation of condition indices for birds. J Wildl Manag 49: 569-575.
72. Johnson MD, Sherry TW, Holmes RT, Marra PP (2006) Assessing habitat quality for a migratory songbird wintering in natural and agricultural habitats. Conserv Biol 20: 1433-1444.
73. Kaiser A (1992) Fat deposition and theoretical flight range of small autumn migrants in southern Germany. Bird Study 39: 96-110.
74. Kaiser A (1993) A new multi-category classification of subcutaneous fat deposits of songbirds. J Field Ornithol 64: 246-255.
75. Kotiaho JS (1999) Estimating fitness: comparison of body condition indices revisited. Oikos 87: 399-400.
76. Krementz DG, Pendleton GW (1990) Fat scoring-sources of variability. Condor 92: 500-507.
77. Lanctot RB, Weatherhead PJ, Kempenaers B, Scribner KT (1998) Male traits, mating tactics and reproductive success in the buff-breasted sandpiper, Tryngites subruficollis. Anim Behav 56: 49-432.
78. Landys-Ciannelli MM, Piersma T, Jukema J (2003) Strategic size changes of internal organs and muscle tissue in the bar-tailed godwit during fat storage on a spring stop over site. Funct Ecol 17: 151-159.
79. Leafloor JO, Thompson JE, Ankney CD (1996) Body mass and carcass composition of fall migrant oldsquaws. Wilson Bull 108: 567-572.
80. Lindstrom A, Kvist A, Piersma T, Dekinga A, Dietz MW (2000) Avian pectoral muscle size rapidly tracks body mass changes during flight, fasting and fuelling. J Exp Biol 203: 913-919.
81. Lozano GA, Handford PT (1995) A test of an assumption of delayed plumage maturation hypotheses using female tree swallows. Wilson Bull 107: 153-164.
82. Lundgren B, Hedenstrom A, Pettersson J (1995) Correlation between some body components and visible fat index in the willow warbler Phylloscopus trochilus (L.). Ornis Svec 5: 75-79.
83. Madsen J, Klaassen M (2006) Assessing body condition and energy budget components by scoring abdominal profiles in free-ranging pink-footed geese Anser brachyrhynchus. J Avian Biol 37: 283-287.
84. Madsen J, Riget F (2007) Do embedded shotgun pellets have a chronic effect on body condition of pink-footed geese? J Wildl Manag 71: 1427-1430.
85. Mann FE, Sedinger JS (1993) Nutrient-reserve dynamics and control of clutch size in northern pintails breeding in Alaska. Auk 110: 264-278.
86. Marshall SD, Jakob EM, Uetz GW (1999) Re-estimating fitness: can scaling issues confound condition indices? Oikos 87: 401-402.
87. Meijer T, Rozman J, Schulte M, StachDreesmann C (1996) New findings in body mass regulation in zebra finches (Taeniopygia guttata) in response to photoperiod and temperature. J Zool 240: 717-734.
88. Merila J, Wiggins DA (1995) Offspring number and quality in the blue tit: a quantitative genetic approach. J Zool 237: 615-623.
89. Miller MR (1989) Estimating carcass fat and protein in northern pintails during the nonbreeding season. J Wildl Manag 53: 123-129.
90. Miller MW, Aradis A, Landucci G (2003) Effects of fat reserves on annual apparent survival of blackbirds Turdus merula. J Anim Ecol 72: 127-132.
91. Moller AP, Szep T (2002) Survival rate of adult barn swallows Hirundo rustica in relation to sexual selection and reproduction. Ecology 83: 2220-2228.
92. Moriguchi S, Amano T, Ushiyama K, Fujita G, Higuchi H (2006) The relationship between abdominal profile index and body condition of greater white-fronted geese Anser albifrons. Ornithol Sci 5: 193-198.
93. Moser TJ, Rusch DH (1988) Indices of structural size and condition of Canada geese. J Wildl Manag 52: 202-208.
94. Muraoka Y, Schulze CH, Pavlicev M, Wichmann G (2009) Spring migration dynamics and sex-specific patterns in stopover strategy in the wood sandpiper Tringa glareola. J Ornithol 150: 313-319.
95. Newton SF (1993) Body condition of a small passerine bird-ultrasonic assessment and significance in overwinter survival. J Zool 229: 561-580.
96. Owen M (1981) Abdominal profile-a condition index for wild geese in the field. J Wildl Manag 45: 227-230.
97. Perdeck AC (1985) Methods of predicting fat reserves in the coot. Ardea 73: 139-146.
98. Petrie SA (2005) Spring body condition, moult status, diet and behaviour of white-faced whistling ducks (Dendrocygna viduata) in northern South Africa. Afr Zool 40: 83-92.
99. Phillips RA, Furness RW (1998) Repeatability of breeding parameters in arctic skuas. J Avian Biol 29: 190-196.
100. Piersma T (1984) Estimating energy reserves of great crested grebes Podicepscristatus on the basis of body dimensions. Ardea 72: 119-126.
101. Piersma T (1988) Body size, nutrient reserves and diet of red-necked and slavonian grebes Podiceps grisegena and P. auritus on Lake Usselmeer, The Netherlands. Bird Study 35: 13-24.
102. Piersma T, Davidson NC (1991) Confusions of mass and size. Auk 108: 441-443.
103. Piersma T, Jukema J (2002) Contrast in adaptive mass gains: Eurasian golden plovers store fat before midwinter and protein before prebreeding flight. Proc R Soc Lond B 269: 1101-1105.
104. Piersma T, van Brederode NE (1990) The estimation of fat reserves in coastal waders before their departure from Northwest Africa in spring. Ardea 78: 221-236.
105. Piersma T, Gudmundsson GA, Lilliendahl K (1999) Rapid changes in the size of different functional organ and muscle groups during refueling in a long-distance migrating shorebird. Physiol Biochem Zool 72: 405-415.
106. Pitt JA, Lariviere S, Messier F (2006) Condition indices and bioelectrical impedance analysis to predict body condition of small carnivores. J Mamm 87: 717-722.
107. Potti J (1998) Variation in the onset of incubation in the pied flycatcher (Ficedula hypoleuca): fitness consequences and constraints. J Zool 245: 335-344.
108. Reinecke KJ, Stone TL, Owen RB Jr (1982) Seasonal carcass composition and energy balance of female black ducks in Maine. Condor 84: 420-426.
109. Rising JD, Somers KM (1989) The measurement of overall body size in birds. Auk 106: 666-674.
110. Robinson S, Chiaradia A, Hindell MA (2005) The effect of body condition on the timing and success of breeding in little penguins Eudyptula minor. Ibis 147: 483-489.
111. Rogers CM (1987) Predation risk and fasting capacity-do wintering birds maintain optimal body-mass. Ecology 68: 1051-1061.
112. Rogers CM (1991) An evaluation of the method of estimating body-fat in birds by quantifying visible subcutaneous fat. J Field Ornithol 62: 349-356.
113. Rogers CM (2003) New and continuing issues with using visible fat classes to estimate fat stores of birds. J Avian Biol 34: 129-133.
114. Rogers CM, Smith JNM (1993) Life-history theory in the nonbreeding period-trade-offs in avian fat reserves. Ecology 74: 419-426.
115. Schamber JL, Esler D, Flint PL (2009) Evaluating the validity of using unverified indices of body condition. J Avian Biol 40: 49-56.
116. Schulte-Hostedde AI, Zinner B, Millar JS, Hickling GJ (2005) Restitution of mass-size residuals: validating body condition indices. Ecology 86: 155-163.
117. Schwilch R, Grattarola A, Spina F, Jenni J (2002) Protein loss during long-distance migratory flight in passerine birds: adaptation and constraint. J Exp Biol 205: 687-695.
118. Seewagen CL (2008) An evaluation of condition indices and predictive models for noninvasive estimates of lipid mass of migrating common yellowthroats, ovenbirds, and Swainson's thrushes. J Field Ornithol 79: 80-86.
119. Senar JC, Copete JL, Martin AJ (1997) Behavioural and morphological correlates of variation in the extent of postjuvenile moult in the siskin Carduelis spinus. Ibis 140: 661-669.
120. Skagen SK, Knopf FL, Cade BS (1993) Estimation of lipids and lean mass of migrating sandpipers. Condor 95: 944-956.
121. Smith LM, Sheeley DG, Wester DB (1992) Condition models for wintering northern pintails in the southern high plains. Gt Basin Nat 52: 226-231.
122. Sparling DW, Barzen JA, Lovvorn JR, Serie JR (1992) An evaluation of regression methods to estimate nutritional condition of canvasbacks and other water birds. Biological Reports 3. US Department of the Interior, Fish and Wildlife Service, Washington, DC.
123. Spengler TJ, Leberg PL, Barrow WC (1995) Comparison of condition indexes in migratory passerines at a stopover site in coastal Louisiana. Condor 97: 438-444.
124. Stauss M, Segelbacher G, Tomiuk J, Bachmann L (2005) Sex ratio of Parus major and P. caeruleus broods depends on parental condition and habitat quality. Oikos 109: 367-373.
125. Swanson DL, Liknes ET, Dean KL (1999) Differences in migratory timing and energetic condition among sex/age classes in migrant ruby-crowned kinglets. Wilson Bull 111: 61-69.
126. Thompson JE, Drobney RD (1996) Nutritional implications of molt in male canvasbacks: variation in nutrient reserves and digestive tract morphology. Condor 98: 512-526.
127. Thompson CF, Flux JEC (1988) Body-mass and lipid-content at nest-leaving of European starlings in New Zealand. Ornis Scand 19: 1-6.
128. Tinbergen JM, Verhulst S (2000) A fixed energetic ceiling to parental effort in the great tit? J Anim Ecol 69: 323-334.
129. Totzke U, Fenske M, Huppop O, Raabe H, Schach N (1999) The influence of fasting on blood and plasma composition of herring gulls (Larus argentatus). Physiol Bioch Zool 72: 426-437.
130. Tsvey A, Bulyuk VN, Kosarev V (2007) Influence of body condition and weather on departures of first-year European robins, Erithacus rubecula, from an autumn migratory stopover site. Behav Ecol Sociobiol 61: 1665-1674.
131. Tu YK, Clerehugh V, Gilthorpe MS (2004) Ratio variables in regression analysis can give rise to spurious results: illustration from two studies in period ontology. J Dent 32: 143-151.
132. Tveraa T, Saether B-E, Aanes R, Erikstad KE (1998) Regulation of food provisioning in the antarctic petrel; the importance of parental body condition and chick body mass. J Anim Ecol 67: 699-704.
133. van der Meer J, Piersma T (1994) Physiologically inspired regression models for estimating and predicting nutrient stores and their composition in birds. Physiol Zool 67: 305-329.
134. Warnock N, Bishop MA (1998) Spring stopover ecology of migrant western sandpipers. Condor 100: 456-467.
135. Weatherhead PJ, Brown GP (1996) Measurement versus estimation of condition in snakes. Can J Zool 74: 1617-1621.
136. Weimerskirch H, Cherel Y (1998) Feeding ecology of short-tailed shearwaters: breeding in Tasmania and foraging in the Antarctic? Mar Ecol Prog Ser 167: 261-274.
137. Wendeln H, Becker PH (1999) Effects of parental quality and effort on the reproduction of common terns. J Anim Ecol 68: 205-214.
138. Whyte RJ, Bolen EG (1984) Variation in winter fat depots and condition indexes of mallards. J Wildl Manag 48: 1370-1373.
139. Whyte RJ, Baldassarre GA, Bolen EG (1986) Winter condition of mallards on the Southern High Plains of Texas. J Wildl Manag 50: 52-57.
140. Wiebe LK, Martin K (1998) Costs and benefits of nest cover for ptarmigan: changes within and between years. Anim Behav 56: 1137-1144.
141. Wiebe LK, Wiehn J, Korpimaki E (1998) The onset of incubation in birds: can females control hatching patterns? Anim Behav 55: 1043-1052.
142. Wiersma P, Piersma T (1995) Scoring abdominal profiles to characterize migratory cohorts of shorebirds: an example with red knots. J Field Ornithol 66: 88-98.
143. Wishart RA (1979) Indices of structural size and condition of American wigeon (Anas americana). Can J Zool 57: 2369-2374.
144. Woodall PF (1978) Omental fat-condition index for redbilled teal. J Wildl Manag 42: 188-190.
145. Yerkes T, Hobson KA, Wassenaar LI, Macleod R, Coluccy JM (2008) Stable isotopes (delta D, delta C-13, delta N-15) reveal associations among geographic location and condition of Alaskan northern pintails. J Wildl Manag 72: 715-725.
146. Yosef R, Markovets M, Mitchell L, Tryjanowski P (2006) Body condition as a determinant for stopover in bee-eaters (Merops apiaster) on spring migration in the Arava Valley, southern Israel. J Arid Environ 64: 401-411.