Table 2.

Proportions of atrial structures, estimated from areas in Amira. One specimen from each species was analysed

Structure\species	Mallard	Green woodpecker	Barn swallow
Tissue weight (g)	0,7	0.07	0,005
Sinus venosus	3%	5%	5%
Left sinus horn	5%	7%	7%
RA wall	20%	21%	29%
RA pectinate muscles	8%	11%	8%
Transverse arch	32%	20%	26%
Dorsal ridge	1%	4%	5%
LA shelf	2%	0,2%	0,5%
LA wall	17%	15%	13%
LA pectinate muscles	8%	15%	7%

Values are rounded to whole numbers, except for values less than 1.