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Table 3.

Values for minimum and maximum urine or voided cloacal fluid osmolality in the three main radiations of nectarivorous birds, compared with some granivorous birds of similar size

Osmolality (mosm kg-1)
Minimum (water-loaded)
Average (normally hydrated)
Maximum* (salt-loaded or dehydrated)
SpeciesDietStudy siteUrine/CFValuesTreatment/dietValuesTreatment/dietValuesTreatment/dietReference
Granivores           
    House sparrow (22 g)   325±181 Seed, W 825±196 Seed, 30 h D 5 
    Salt-marsh savannah sparrow (19 g)     577±164 Saltmarsh 7 
    Whitecrowned sparrow (26 g)   476±211 811±167 6 
    House finch (19 g) CF     183±75 Desert, ambient temp. 30±4°C 2 
    House finch (19 g) CF   225 Seed, W 850 Seed, 0.3 mol l-1 NaCl 10 
    Zebra finch (13 g) DS   381±25 Seed, W 1027±24 Seed, 0.8 mol l-1 NaCl 11 
    Zebra finch (13 g) DS     1005±26 Seed, D 11 
Honeyeaters           
    Yellow-throated miner (49 g)     368±47 Arid, autumn 4 
    New Holland honeyeater (20 g) N,I   288±51 Winter (W) 187±26 Mesic, summer (D) 4 
    Red wattlebird (97 g) N,I   191±21 Winter (W) 337±61 Mesic, summer (D) 4 
Hummingbirds           
    Broadtailed hummingbird (3 g) CF 10 Feeders and flowers 54±43 Feeders and flowers 342 Resource competition stress 3 
    Anna's hummingbird (4.5 g) CF 27 ” 53±18 ”   3 
    Costa's hummingbird (3 g) CF 34 ” 57±20 ”   3 
    Blackchinned hummingbird (3 g) CF 30 ” 89±52 ”   3 
    Calliope hummingbird (2.5 g) CF 36 ” 66±27 ”   3 
    Rufous hummingbird (4 g) CF 16 ” 81±77 ” 383 Resource competition stress 3 
    Rufous hummingbird (4 g) CF   100 0.6 mol l-1 sucrose 600 0.6 mol l-1 sucrose+ 8 
         0.2 mol l-1 NaCl, D  
    Rubythroated hummingbird (3 g) CF 10 0.2 mol l-1 sucrose, D     1 
Sunbirds           
    Palestine sunbird (6 g) 15 0.15 mol l-1 sucrose, D 329 1.17 mol l-1 sucrose, D   9 
    Palestine sunbird (6 g) CF 12 0.15 mol l-1 sucrose, D 95 1.17 mol l-1 sucrose, D   9 
    Whitebellied sunbird (9 g) CF 6±2 0.25 mol l-1 sucrose, W 56±61 1 mol l-1 sucrose, D 461±253 2.5 mol l-1 sucrose, D 12 
Osmolality (mosm kg-1)
Minimum (water-loaded)
Average (normally hydrated)
Maximum* (salt-loaded or dehydrated)
SpeciesDietStudy siteUrine/CFValuesTreatment/dietValuesTreatment/dietValuesTreatment/dietReference
Granivores           
    House sparrow (22 g)   325±181 Seed, W 825±196 Seed, 30 h D 5 
    Salt-marsh savannah sparrow (19 g)     577±164 Saltmarsh 7 
    Whitecrowned sparrow (26 g)   476±211 811±167 6 
    House finch (19 g) CF     183±75 Desert, ambient temp. 30±4°C 2 
    House finch (19 g) CF   225 Seed, W 850 Seed, 0.3 mol l-1 NaCl 10 
    Zebra finch (13 g) DS   381±25 Seed, W 1027±24 Seed, 0.8 mol l-1 NaCl 11 
    Zebra finch (13 g) DS     1005±26 Seed, D 11 
Honeyeaters           
    Yellow-throated miner (49 g)     368±47 Arid, autumn 4 
    New Holland honeyeater (20 g) N,I   288±51 Winter (W) 187±26 Mesic, summer (D) 4 
    Red wattlebird (97 g) N,I   191±21 Winter (W) 337±61 Mesic, summer (D) 4 
Hummingbirds           
    Broadtailed hummingbird (3 g) CF 10 Feeders and flowers 54±43 Feeders and flowers 342 Resource competition stress 3 
    Anna's hummingbird (4.5 g) CF 27 ” 53±18 ”   3 
    Costa's hummingbird (3 g) CF 34 ” 57±20 ”   3 
    Blackchinned hummingbird (3 g) CF 30 ” 89±52 ”   3 
    Calliope hummingbird (2.5 g) CF 36 ” 66±27 ”   3 
    Rufous hummingbird (4 g) CF 16 ” 81±77 ” 383 Resource competition stress 3 
    Rufous hummingbird (4 g) CF   100 0.6 mol l-1 sucrose 600 0.6 mol l-1 sucrose+ 8 
         0.2 mol l-1 NaCl, D  
    Rubythroated hummingbird (3 g) CF 10 0.2 mol l-1 sucrose, D     1 
Sunbirds           
    Palestine sunbird (6 g) 15 0.15 mol l-1 sucrose, D 329 1.17 mol l-1 sucrose, D   9 
    Palestine sunbird (6 g) CF 12 0.15 mol l-1 sucrose, D 95 1.17 mol l-1 sucrose, D   9 
    Whitebellied sunbird (9 g) CF 6±2 0.25 mol l-1 sucrose, W 56±61 1 mol l-1 sucrose, D 461±253 2.5 mol l-1 sucrose, D 12 

Diets are: G, granivore; I, insectivore; N, nectarivore.

Data are from field (F) and laboratory (L) studies.

U, urine, collected by cannulation; CF, voided cloacal fluid; DS, dropping supernatant.

Trials are: D, without drinking water or dry natural conditions; W, with ad libitum drinking water.

Values are means ± 1 S.D., where available.

*

Measurements of maximum urine concentrations are limited to diets for which birds maintain measurable levels of urine production, a factor that may particularly affect estimates of the concentrating capacity of granivorous birds. Additionally, spheres of precipitated urates, which do not contribute to measured urinary osmolality, may trap ions(Goldstein and Braun,1989).

1

Beuchat, 1998; 2Calder, 1981; 3Calder and Hiebert,1983, Hiebert and Calder,1986; 4Goldstein and Bradshaw, 1998a; 5Goldstein and Braun,1988; 6Goldstein and Braun, 1989; 7Goldstein et al.,1990; 8Lotz and Martínez del Rio, 2003; 9T. J. McWhorter, C. Martínez del Rio, B. Pinshow and L. Roxburgh, unpublished data; 10Poulson and Bartholomew,1962; 11Skadhauge and Bradshaw, 1974; 12Present study.

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