SUPPORTING INFORMATION
Additional Supporting Information may be found in the online version of this article.
Fig. S1 . Mean annual precipitation δ
2
H isoscape for the general area of the Scaly-sided Merganser study region (based on data from http//:waterisotopes.org).
Table S1.
Full details of the δ 2
H f
, δ 13
C f
and δ
15
N f
(‰) determinations of feathers from Scaly-sided
Merganser analysed in this study.
1

Fig. S1
. Precipitation δ 2
H isoscape for the general area of the Scaly-sided Merganser study region, showing the river catchments named in the text. Depiction based on data from http//:waterisotopes.org.
Kri va
Kie ya vk a
Ma
Av va rg ku ari tov mo ka vk a
Malinovka
Pavlovka
2
Kur

8505
8507
8508
8510
8518
8519
8527
7856
7858
7860
7862
7862
7867
8529
8532
8545
8549
8549
8561
8562
8565
8566
8567
8568
No ring
Table S1.
Full details of the δ 2 H f
, δ 13 C f
and δ 15 N f
(‰) determinations of feathers from Scaly-sided Merganser analysed in this study. “Bird identifier” is the last four digits of the metal ring number to uniquely identify re-captures and multiple determinations. “Age” differentiates AHY (after hatch year) and ASY (after second year) from older birds (ad) based on plumage characteristics defined in the text. “Year” identifies the sampling year (i.e. the sampled feather was grown in the preceding calendar year). Capture River provides the location where the bird was captured and feather sample taken. “Geolocation/nesting moult location” identifies the catchment where these individuals were known to have moulted their flight feathers based on geolocation; locations in italics indicate where females were inferred to have moulted based on their nest site and subsequent brood rearing catchment in the absence of geolocation in the year for which an analysed feather sample was taken. “River water” shows the results of δ 2 H w
(‰) determinations of river water from the same catchments where individuals were known to have moulted, except in the case of the Avvakumovka River for which water samples were not available and values from the adjacent Margaritovka River were substituted (shown in parentheses and italics) . See methods in the text for full details.
Bird Age/sex Year Capture River (where Geolocation/nesting
δ 2 H f
(‰) River water δ 2 H w
(‰)
Identifier feather sample taken) moult location where known
δ 13 C
(‰)
-23.2
δ 15 N
(‰)
12.1
Inferred moult location
Freshwater 6371
7515
7516
7516
7851
7851
Ad f
Ad f
Ad f
Ad f
Ad f
Ad f
2008
2007
2008
2007
2008
2007
Kievka
Pavlovka
Kievka
Kievka
Kievka
Kievka
Kievka
Pavlovka
Kur River
Kievka
Kievka
-78.9
-103.2
-121.1
-121.3
-81.4
-73
-74.4
-92.6
-114.2
-74.4
-74.4
-24.3
-23.7
-20.3
-23.4
-24.5
13.2
13.1
12.0
12.5
12.9
Freshwater
Freshwater
Freshwater
Freshwater
Freshwater
Ad f
Ad f
AHY f
Ad f
Ad f
Ad f
ASY f 2008
Ad f
Ad m
Ad f
Ad f
Ad m
AHY m 2008
AHY m 2008
ASY f
Ad m
Ad f
Ad m
Ad f
ASY f 2012
ATY f 2012
Ad f
Ad f
Ad f
Ad f
2007
2007
2008
2008
2007
2007
2008
2008
2008
2007
2008
2008
2008
2008
2007
2012
2012
2012
2012
2012
Krivaya
Kievka
Kievka
Kievka
Kievka
Kievka
Avvakumovka
Kievka
Kievka
Kievka
Kievka
Kievka
Kievka
Kievka
Kievka
Kievka
Kievka
Malinovka
Kievka
Kievka
Kievka
Avvakumovka
Avvakumovka
Kievka
Avvakumovka
Krivaya
Kievka
Amur estuary
Kievka
Kievka
Avvakumovka
Avvakumovka
Kievka
Avvakumovka
-60.2
-76.2
-123.1
-0.7
-8.6
-83.2
-13.1
-79.2
-107.6
-82
-75.4
-128,5
-92.4
-119,1
-4.6
-97.2
-79.8
-53.8
-85.54
-41.66
-82.93
-87.68
-82.88
-73.45
-85.09 (
(
-69.6
-74.4
-74.4
-74.4
-77.8
(-77.8
-74.4
-77.8
)
)
)
-21.4
-23.5
-21.9
-17.1
-18.0
-23.9
-24.8
-22.5
-28.0
-23.2
-23.2
-25.5
-24.0
-19.2
-16.0
-26.6
-22.9
-14.6
-23.02
-15.99
-24.34
-26.91
-26.34
-24.12
-26.35
10.5
13.0
11.3
15.4
15.1
10.3
13.3
12.4
12.0
12.4
12.5
10.9
12.1
8.6
14.3
10.6
12.3
17.3
12.06
18.06
12.11
11.78
11.53
11.96
11.59
Freshwater
Freshwater
Freshwater
Marine/brackish
Marine/brackish
Freshwater
Marine/brackish
Freshwater
Freshwater
Freshwater
Freshwater
Freshwater
Freshwater
Freshwater
Marine/brackish
Freshwater
Freshwater
?Marine/brackish
Freshwater
Marine/brackish
Freshwater
Freshwater
Freshwater
Freshwater
Freshwater
3

4