304 



ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1932 



7. They reduce the amount of twisting that is required in flapping 

 flight to align the outer parts of a wing reasonably near the gradient 

 of the air stream, which is much steeper at the tip than near the 

 shoulder. 



8. The final spreading of a wing, which opens the slots, appears to 

 be done automatically, air reaction dragging the separated feathers 

 forward when the incidence is sufficiently high. 



9. Overspreading of a wing, to the extent that gaps would appear 

 between the feathers on the body side of the inner extremities of the 

 slots, is prevented by means of special friction surfaces on the over- 

 lapping parts of the feathers. 



10. The wings of all birds found in the British Isles possess a 

 second antistalling device situated just outside the wrist joint, in 

 the shape of the bastard wing. Its size varies in different species 

 from about one-tenth of the length of the wing to about three-tenths. 

 In form, action, and effect, it more closely resembles the Handley- 

 Page auxiliary airfoil than wing-tip slots do. 



Some flight characteristics 



Long-tailed tit_. 



Wren fledgling 



Coal tit 



Wren (adult) 



Blue tit 



Marsh tit... 



Goldflnch 



Robin 



Swallow (fledgling)... 



Spotted flycatcher 



Gray wagtail 



Great tit 



Wheatear. 



Blackcap 



Linnet 



House sparrow (hen).. 



Pied wagtail 



Reed bunting 



Swallow (adult) 



Hedge sparrow 



Yellow hammer.. 



Bullfinch (hen) 



Chaffinch (hen) 



House sparrow (cock). 



Green-finch 



Wryneck 



Skylark 



Jack snipe.. 



Song thrush 



Nightjar 



Hoopoe.. 



Starling 



Golden plover 



Blackbird (hen) 



Quail 



Common snipe 



Sparrow hawk (hen) . . 



Scops owl 



Mistle thrush 



Weight 

 (ounces) 



0.25 

 .31 

 .33 

 .36 

 .37 

 .38 

 .44 

 .50 

 .50 

 .50 

 .50 

 .69 

 .72 

 .75 

 .75 

 .75 

 .75 

 .75 

 .81 

 .81 

 .87 



1.00 

 1.12 

 1.37 

 1.50 

 2.00 

 2.31 

 2.31 

 2.50 

 2.50 

 3.00 

 3.50 

 4.00 

 4.00 

 4.00 

 4.25 

 4.25 



Wing 



loading 



(pounds 



per 



square 

 foot) 



0.26 

 .47 

 .39 

 .40 

 .33 

 .36 

 .36 

 .39 

 .35 

 .35 

 .44 

 .49 

 .36 

 .62 

 .54 

 .43 

 .41 

 .43 

 .34 

 .67 

 .56 

 .53 

 .54 

 .58 

 .55 

 .08 

 .50 

 .93 

 .77 

 .40 

 .55 

 .75 



1.18 

 .87 



1.76 



1.23 

 .45 

 .64 



1.05 



Span 

 loading 

 (ounces 

 per foot) 



0.46 



.79 



.57 



.92 



.00 



.60 



.69 



.71 



.68 



.69 



.70 



.97 



.86 



1.10 



1.00 



1.10 



.85 



.95 



.80 



1.22 



1.04 



1.16 



1.10 



1.18 



1.25 



1.37 



1.40 



1.70 



2.00 



1.30 



1.06 



2.00 



2.10 



2.90 



3.20 



2.75 



2.00 



2.38 



3.10 



Span 

 (inches) 



0.50 



4.70 



6.90 



4.70 



7.40 



7.60 



7.70 



8.40 



10.25 



9.70 



9.00 



8.50 



10.00 



8.00 



9.00 



8.00 



10.60 



9.50 



12.50 



8.00 



10.00 



9.00 



9.60 



10.20 



10.75 



12.00 



13.00 



14.20 



13.80 



21.50 



18.00 



15.00 



17.00 



14.50 



15.00 



17.50 



24.00 



21.40 



16.50 



Aspect 

 ratio 



1.85 



1.70 



2.20 



1.70 



2.20 



2.001 



2.35 



1.94 



2.95 



2.45 



2.27 



1.68 



2.20 



2.30 



2.32 



2.50 



2.37 



2.05 



3.50 



1.75 



2.20 



2.05 



2.30 



2.30 



2.50 



2.80 



2.60 



3.30 



2.46 



3.40 



2.06 



2.90 



3.60 



2.10 



3.17 



3.78 



2.65 



2.36 



2.40 



Wing- 

 tip slot 

 factor 



1.46 

 .77 



1.00 

 .67 



1.10 

 .98 

 .54 

 .82 



.17 

 .45 

 1.36 



.84 

 .42 

 .45 

 .45 

 .47 

 .76 



.69 

 .75 

 .36 

 .73 

 .58 

 .62 

 .18 

 .60 



.55 

 .36 

 1.00 

 .21 



1.22 

 .31 

 .72 



Wrist- 

 slot fac- 

 tor 



0.15 

 .24 

 .13 

 .18 

 .16 

 .17 

 .15 

 .18 

 .17 

 .16 

 .16 

 .20 

 .15 

 .17 

 .16 

 .16 

 .18 

 .16 

 .13 

 .18 

 .17 

 .19 

 .18 

 .17 

 .17 

 .12 

 .16 

 .16 

 .17 

 .16 

 .16 

 .16 

 .12 

 .20 

 .20 

 .16 

 .27 

 .20 

 .18 



Number 

 of wing- 

 tip slots 



I The wrist-slot factor of a young song thrush on its first day out of the nest was found to bo 0.3. 



