屏科大野保所鳥類生態研究室

接續 科學家對河烏了解多少(上)

野生動物保育彙報與通訊 第16卷第4期20-33頁

http://wildmic.npust.edu.tw/ptrc/index.html

 五、水質汙染

    水質對河烏影響的研究最早也是從英國開始的。因空氣汙染導致的酸沉降現象(acid deposition)使得河水變酸，在這些酸化溪流白喉河烏的繁殖密度較低，懷疑是溪流酸化使水生昆蟲數量減少(Ormerod et al., 1985b; Ormerod et al., 1986)。科學家也發現低pH值會讓河烏缺鈣，導致蛋殼厚度變薄(Ormerod et al., 1988; Nybø et al., 1997)。河水酸化對河烏繁殖表現也有很大的影響，會導致繁殖時間較晚、窩卵數較低、幼鳥成長較慢而且不繁殖第二窩，繁殖前期成鳥體重較輕、血鈣濃度較低，可能是因為酸化溪流食物缺乏的緣故(Ormerod et al., 1991; Vickery, 1992)。接著Ormerod and Tyler (1989)用1984年104個樣點的水質資料模擬到2010年時，硫酸鹽濃度減少0-90%對河烏的影響，結果顯示要減少超過50%才能避免河烏數量下降。Tyler and Ormerod (1992)將上述的研究做了一個總整理，並且認為酸化溪流的重金屬和有機氯殺蟲劑含量較低，所以不是這兩樣的影響。Buckton et al. (1998)1984和1995年在英國威爾斯各調查一次河烏數量、酸鹼值和水生昆蟲，1995年所有樣點pH值平均上升0.12，但毛翅目數量下降，且平均調查數量少於1984年，不能排除河烏數量在下降的可能性。

    除了溪流酸化，有機氯殺蟲劑也對河烏造成影響，科學家在英國威爾斯、蘇格蘭和愛爾蘭收集未受精或未孵化的蛋，少數的蛋驗出汞、六氯環已烷(HCH)或六氯苯(HCB)，大多數都驗出阿特靈代謝物(HEOD)、DDE(DDT的衍生物)和多氯聯苯(PCBs) (Ormerod and Tyler, 1990; Ormerod and Tyler, 1992; O'Halloran et al., 2003)。Ormerod and Tyler (1993a)進一步分析不同流域的濃度差異，從PCBs的濃度分布推測汙染源是沿海工業區，而綿羊密度越高HEOD濃度越高，可能跟浴羊藥劑的成分有關。由於PCBs對野外燕雀目鳥類影響的研究還非常，Ormerod et al. (2000)調查英國威爾斯一條被汙染的河川，發現河烏蛋的PCBs濃度是其他地區的4-20倍，不過繁殖表現卻跟其他乾淨河川相同，幼鳥回收率也很接近，因此認為PCBs在0.49(平均值)–1.29(第三四分位數) mg/g (濕重)時對河烏繁殖和存活率尚無影響。

    還記得那位研究美洲河烏遷移策略的Morrissey嗎?她的團隊也發現留鳥和遷移鳥的蛋中汙染物殘留的程度不同，留鳥的有機率殺蟲劑、PCBs和汞濃度都高於遷徙鳥，以穩定同位素追蹤發現留鳥吃小鮭魚(42%)多於遷徙鳥(21%)，所以鮭魚可能是汙染源(Morrissey et al., 2004b;2005)。於是她們進一步調查不同密度的鮭魚洄游是否會影響河烏蛋的汙染物和碳、氫同位素組成，結果水生昆蟲和河烏蛋的碳同位素隨鮭魚密度增加而增加，氫則沒有趨勢。溴化阻燃劑(PBDEs)、氯丹化合物(chlordane compounds)和DDT濃度跟鮭魚密度有關，汞、氯苯(chlorobenzenes)和PCBs則是跟河烏的營養位階有關(Morrissey et al., 2011)。

    採礦是另一個河川汙染的原因，Strom et al. (2002)在美國科羅拉多礦區，發現當地美洲河烏的ALAD(aminolevulinic acid dehydratase)酵素活性比其他地區低50%，而且血鉛濃度和ALDA酵素活性負相關，因此ALDA酵素活性可作為鉛中毒的指標。在加拿大的哥倫比亞，因採礦使硒(Se)的濃度在水和土壤中不斷上升，部分地區已經到了有害的程度，Harding et al. (2005)檢驗河烏和斑鷸(Actitis macularia)蛋的硒濃度，兩種鳥蛋的硒濃度都比預期還要低，可能是溪流生態中對硒的生物轉化率較低，兩者的繁殖表現也都未受影響。

    Sorace et al. (2002)認為如果河烏是水質的指標物種，對水質改變的反應會很敏感。他們調查義大利的47條河川中，乾淨的河川93.3%有河烏，受汙染的河川93.7%沒有河烏，有50%的河川以前有河烏但現在沒有，所以河烏的分布範圍正在縮減。Feck and Hall Jr (2004)在美國懷俄明州調查幾種常用水質指標跟有無河烏的相關性，結果都只有輕度相關，只有跟蜉蝣目數量高度相關，而領域大小和繁殖表現則難以用水質預測，因此目前常用的水質指標無法明確反應河烏的需求。

六、褐河烏文獻回顧

    目前找到最早關於褐河烏的研究是在日本，Hansen (1981)觀察了日本的褐河烏和美國的美洲河烏各一年，記錄和比較這兩種的求偶和領域行為，提到兩者都有一夫多妻制。同年發表的(Hashiguchi and Yamagishi, 1981)則注意到日本的褐河烏在冬季(繁殖季初期)會有明顯的威嚇和攻擊行為，某些個體有固定的領域，某些則四處遊走。Eguchi (1990)在日本熊本縣觀察褐河烏的覓食行為，發現河烏潛水可以捕捉較大型的獵物，但也比較耗費能量，因此只有在育雛時較常潛水。Kofuji et al. (1993)測量3對褐河烏糞便中的雌激素和睪固酮含量，母鳥的雌激素和睪固酮只有交配期最高，持續一星期左右，公鳥的睪固酮則是從冬末到繁殖季結束都維持在高點。

    中國對褐河烏的繁殖也有初步的描述，吴建平和刘相林(1994)在黑龍江省觀察育雛行為，同樣記錄窩卵數、孵卵期和育雛期，當地河烏4月初開始繁殖，領域行為不明顯，卵和雛鳥被觸動時，親鳥不會棄巢，17日齡雛鳥一天會被餵食28次，餵雛高峰每小時餵食4.1次(註:還真少)。

    台灣的褐河烏研究相對於國外是起步較晚，陳炤杰是台灣最早進行河烏研究的學者，他的研究發現急流區的水生昆蟲生物量較高，河烏也花較多的時間在急流區覓食，因此河烏領域長度(1045 ±165 m)跟急流的比例、水生昆蟲生物量以及海拔負相關(陳炤杰, 1989; Chen and Wang, 2010)。

    自2003年起，雪霸國家公園委託屏東科技大學的孫元勳教授調查櫻花鉤吻鮭(Oncorhynchus masou formosanus)的天敵，加上後續的七家灣溪長期生態研究計畫，開啟了褐河烏研究的新契機。孫元勳(2007)調查發現河烏是櫻花鉤吻鮭幼鮭的重要天敵，經過推算一對河烏在育雛期可捕捉396條小鮭魚，約占幼鮭死亡率的21-23%。在七家灣溪河烏育雛期的食性選擇上，河烏偏好體型較大的魚類和毛翅目昆蟲，尤其是育雛後期偏好的現象更加明顯，可能是育雛初期幼鳥嘴巴還太小，無法吃過大的食物(Chiu et al., 2009)。近年來七家灣溪發生多次劇烈的洪水事件，研究團隊調查2003-2006年洪水、河烏和水生昆蟲之間的相關性，結果顯示河烏的數量跟水生昆蟲彼此間有強烈相關，但都跟溪水流量負相關，因此洪水會減少水生昆蟲進而影響河烏族群(Chiu et al., 2008; 丘明智，2009)。

    洪孝宇等(2011)描述七家灣溪河烏的繁殖生物學，當地河烏1月中開始繁殖，窩卵數平均4.1(±0.3)枚，雌雄共同築巢和育雛，孵卵則由雌鳥獨自進行，且雄鳥不提供食物。育雛期的餵食頻度以上午8-9時最低(12次/h)，下午5時最高(32次/h)，繁殖失敗原因可分為天候因素和天敵攻擊兩類。比較洪水前後兩年的河烏繁殖表現，洪水隔年的巢數和繁殖成功率均遠低於洪水前，可能是水生昆蟲量尚未回復所致。洪孝宇等(2012)記錄了一次2004年七家灣溪發生洪水時，部分河烏到鄰近的有勝溪避難，使有勝溪的河烏密度異常增加的事件。

結語

    河烏因為棲地專一性強、位在食物鏈上層、容易調查和繫放、線性領域容易量化等優點，成為非常適合做生態研究和環境汙染監測的模式物種(model species)，白喉河烏和美洲河烏都已經累積大量的研究成果。近年來氣候變遷的危機持續升高，根據國科會的報告，最近十年不但強烈颱風侵襲台灣的比例增加，豪雨的天數也增多(許晃雄等，2011)，如此劇烈且頻繁的洪水對溪流生態的衝擊非常值得關注，加上台灣地形山高水急，部分地區乾濕季節分明，溪流狀況跟國外相當不同，因此台灣的褐河烏研究其實還有很大的空間可以努力。

參考文獻

丘明智，2009。武陵地區洪流及河烏與溪流昆蟲之關係。國立中興大學昆蟲學系博士論文。
吴建平、刘相林，1994。褐河乌繁殖观察。东北林业大学学报22:37-40。
洪孝宇、陳惠玲、郭智筌、曾建偉、孫元勳，2011。七家灣溪河烏(Cinclus pallasi)的繁殖生物學。國家公園學報21:30-36。
洪孝宇、郭智筌、孫元勳，2012。颱風來了!七家灣溪河烏避難記。自然保育季刊77:63-68。
陳炤杰，1989。河烏繁殖領域與棲地關係之研究。國立臺灣師範大學生物研究所碩士論文。
許晃雄、陳正達、盧孟明、陳永明、周佳、吳宜昭。2011。臺灣氣候變遷科學報告2011。行政院國家科學委員會。
孫元勳，2007。是誰在偷吃國寶魚?科學發展417:35-39。
Andersson, J. S., and S. A. L. Wester. 1973. Sex and age ratios of wintering Dippers Cinclus c. cinclus (L.). Ornis Scandinavica:153-156.
Andersson, S., and S. Wester. 1976. Långåterfynd av nordiska strömstarar Cinclus c. cinclus. Vår Fågelvärld 35:279-286.
Bakus, G. J. 1959a. Observations on the life history of the dipper in Montana. The Auk 76:190-207.
Bakus, G. J. 1959b. Territoriality, movements, and population density of the dipper in Montana. The Condor 61:410-425.
Buckton, S. T., P. A. Brewin, A. Lewis, P. Stevens, and S. J. Ormerod. 1998. The distribution of dippers, Cinclus cinclus (L.), in the acid-sensitive region of Wales 1984–95. Freshwater Biology 39:387-396.
Chen, C. C., and Y. Wang. 2010. Relationships between stream habitat and breeding territory length of the Brown Dipper (Cinclus pallasii) in Taiwan. Journal of Ornithology 151:87-93.
Chiu, M. C., M. H. Kuo, Y. H. Sun, S. Y. Hong, and H. C. Kuo. 2008. Effects of flooding on avian top-predators and their invertebrate prey in a monsoonal Taiwan stream. Freshwater Biology 53:1335-1344.
Chiu, M. C., M. H. Kuo, C. S. Tzeng, C. H. Yang, C. C. Chen, and Y. H. Sun. 2009. Prey selection by breeding Brown Dippers Cinclus pallasii in a Taiwanese mountain stream. Zoological Studies 48:761-768.
D'Amico, F., E. Boitier, and G. Marzolin. 2003. Timing of onset of breeding in three different Dipper Cinclus cinclus populations in France: Timing of breeding varies widely. Bird Study 50:189-192.
D’Amico, F., and G. Hemery. 2003. Calculating census efficiency for river birds: a case study with the White‐throated Dipper Cinclus cinclus in the Pyrénées. Ibis 145:83-86.
Eguchi, K. 1990. The choice of foraging methods of the Brown Dipper, Cinclus pallasii (Aves: Cinclidae). Journal of Ethology 8:121-127.
Feck, J., and R. O. Hall Jr. 2004. Response of American dippers (Cinclus mexicanus) to variation in stream water quality. Freshwater Biology 49:1123-1137.
Galbraith, H., and S. J. Tyler. 1982. The movements and mortality of the Dipper as shown by ringing recoveries. Ringing & Migration 4:9-14.
Garwood, J. M., K. L. Pope, R. M. Bourque, and M. D. Larson. 2009. High mountain lakes provide a seasonal niche for migrant American Dippers. Wilson Journal of Ornithology 121:600-609.
Gillis, E. A., D. J. Green, H. A. Middleton, and C. A. Morrissey. 2008. Life history correlates of alternative migratory strategies in American Dippers. Ecology 89:1687-1695.
Hann, H. W. 1950. Nesting behavior of the American Dipper in Colorado. The Condor 52:49-62.
Hansen, D. 1981. Polygyny adaptive alternative monogamy 2 species dippers cinclus mexicanus and cinclus pallasii. Journal of The Yamashina Institute for Ornithology 13:7-35.
Harding, L. E., M. Graham, and D. Paton. 2005. Accumulation of selenium and lack of severe effects on productivity of American dippers (Cinclus mexicanus) and spotted sandpipers (Actitis macularia). Archives of Environmental Contamination and Toxicology 48:414-423.
Harvey, B. C., and C. D. Marti. 1993. The impact of dipper, Cinclus mexicanus, predation on stream benthos. Oikos:431-436.
Hashiguchi, D., and S. Yamagishi. 1981. Dispersion pattern and territorial behavior of the wintering Brown Dipper, Cinclus pallasii. Japanese Journal of Ecology 31:161-170.
Hegelbach, J. 2001. Water temperature and phytophenology indicate the earlier onset of oviposition in Eurasian Dipper (Cinclus cinclus) from the Swiss Lowlands. Journal für Ornithologie 142:284-294.
Jenkins, R. K. B., and S. J. Ormerod. 1996. The influence of a river bird, the dipper (Cinclus cinclus), on the behaviour and drift of its invertebrate prey. Freshwater Biology 35:45-56.
Kofuji, H., M. Kanda, and T. Oishi. 1993. Breeding cycles and fecal gonadal steroids in the Brown Dipper Cinclus pallasii. General and Comparative Endocrinology 91:216-223.
Loegering, J. P., and R. G. Anthony. 2006. Nest-site selection and productivity of American Dippers in the Oregon coast range. The Wilson Journal of Ornithology 118:281-294.
Logie, J. W., D. M. Bryant, D. L. Howell, and J. A. Vickery. 1996. Biological significance of UK critical load exceedance estimates for flowing waters: assessments of dipper Cinclus cinclus populations in Scotland. Journal of Applied Ecology:1065-1076.
Loison, A., B.-E. Sæther, K. Jerstad, and O. W. Rostad. 2002. Disentangling the sources of variation in the survival of the European dipper. Journal of Applied Statistics 29:289-304.
Lundberg, P., A. Bergman, and H. Olsson. 1981. On the ecology of wintering Dippers (Cinclus cinclus) in northern Sweden. Journal of Ornithology 122:163-172.
Mackas, R. H., D. J. Green, I. B. J. Whitehorne, E. N. Fairhurst, H. A. Middleton, and C. A. Morrissey. 2010. Altitudinal migration in American Dippers (Cinclus mexicanus): Do migrants produce higher quality offspring? Canadian journal of zoology 88:369-377.
Marzolin, G. 2002. Influence of the mating system of the Eurasian Dipper on sex-specific local survival rates. The Journal of wildlife management:1023-1030.
Marzolin, G., A. Charmantier, and O. Gimenez. 2011. Frailty in state-space models: application to actuarial senescence in the Dipper. Ecology 92:562-567.
Middleton, H. A., C. A. Morrissey, and D. J. Green. 2006. Breeding territory fidelity in a partial migrant, the American dipper Cinclus mexicanus. Journal of Avian Biology 37:169-178.
Morrissey, C. A. 2004. Effect of altitudinal migration within a watershed on the reproductive success of American dippers. Canadian journal of zoology 82:800-807.
Morrissey, C. A., L. I. Bendell-Young, and J. E. Elliott. 2004a. Seasonal trends in population density, distribution, and movement of American dippers within a watershed of southwestern British Columbia, Canada. Condor 106:815-825.
Morrissey, C. A., L. I. Bendell‐Young, and J. E. Elliott. 2004b. Linking contaminant profiles to the diet and breeding location of American dippers using stable isotopes. Journal of Applied Ecology 41:502-512.
Morrissey, C. A., L. I. Bendell‐Young, and J. E. Elliott. 2005. Assessing trace‐metal exposure to American dippers in mountain streams of southwestern British Columbia, Canada. Environmental Toxicology and Chemistry 24:836-845.
Morrissey, C. A., I. L. Pollet, S. J. Ormerod, and J. E. Elliott. 2011. American dippers indicate contaminant biotransport by Pacific salmon. Environmental Science & Technology 46:1153-1162.
Nilsson, A. L. K., E. Knudsen, K. Jerstad, O. W. Røstad, B. Walseng, T. Slagsvold, and N. C. Stenseth. 2011. Climate effects on population fluctuations of the white‐throated dipper Cinclus cinclus. Journal of Animal Ecology 80:235-243.
Nybø, S., M. Staurnes, and K. Jerstad. 1997. Thinner eggshells of dipper (Cinclus cinclus) eggs from an acidified area compared to a non-acidified area in Norway. Water, Air, & Soil Pollution 93:255-266.
O'Halloran, J., S. Irwin, S. Harrison, P. Smiddy, and B. O'Mahony. 2003. Mercury and organochlorine content of Dipper Cinclus cinclus eggs in south-west Ireland: trends during 1990-1999. Environmental Pollution 123:85-93.
O'Halloran, J., P. Smiddy, and B. O'Mahony. 2000. Movements of Dippers Cinclus cinclus in southwest Ireland. Ringing & Migration 20:147-151.
Obermeyer, K. E., A. Hodgson, and M. F. Willson. 1999. American Dipper, Cinclus mexicanus, foraging on Pacific salmon, Oncorhynchus sp., eggs. Canadian Field-Naturalist 113:288-290.
Obermeyer, K. E., K. S. White, and M. F. Willson. 2006. Influence of salmon on the nesting ecology of American dippers in southeastern Alaska. Northwest Science 80:26.
Ormerod, S., and S. Tyler. 1990. Environmental pollutants in the eggs of Welsh Dipper; Cinclus cinclus: a potential monitor of organochlorine and mercury contamination in upland rivers. Bird Study 37:171-176.
Ormerod, S., and S. Tyler. 1993a. Further studies of the organochlorine content of Dipper Cinclus cinclus eggs: local differences between Welsh catchments. Bird Study 40:97-106.
Ormerod, S. J. 1985. The diet of breeding Dippers Cinclus cinclus and their nestlings in the catchment of the River Wye, mid‐Wales: a preliminary study by faecal analysis. Ibis 127:316-331.
Ormerod, S. J., N. Allenson, D. Hudson, and S. J. Tyler. 1986. The distribution of breeding dippers (Cinclus cinclus (L.); Aves) in relation to stream acidity in upland Wales. Freshwater Biology 16:501-507.
Ormerod, S. J., M. A. Boilstone, and S. J. Tyler. 1985a. Factors influencing the abundance of breeding Dippers Cinclus cinclus in the catchment of the River Wye, mid‐Wales. Ibis 127:332-340.
Ormerod, S. J., K. R. Bull, C. P. Cummins, S. J. Tyler, and J. A. Vickery. 1988. Egg mass and shell thickness in dippers Cinclus cinclus in relation to stream acidity in Wales and Scotland. Environmental Pollution 55:107-121.
Ormerod, S. J., J. O'Halloran, S. D. Gribbin, and S. J. Tyler. 1991. The ecology of Dippers Cinclus cinclus in relation to stream acidity in upland Wales: breeding performance, calcium physiology and nestling growth. Journal of Applied Ecology 28:419-433.
Ormerod, S. J., E. Svein, and E. G. Leif. 1987. The diet of breeding dippers Cinclus cinclus cinclus and their nestlings in southwestern Norway. Holarctic Ecology 10:201-205.
Ormerod, S. J., and S. J. Tyler. 1986. The diet of dippers Cinclus cinclus wintering in the catchment of the River Wye, Wales. Bird Study 33:36-45.
Ormerod, S. J., and S. J. Tyler. 1989. Long-term change in the suitability of Welsh streams for Dippers Cinclus cinclus as a result of acidification and recovery: a modelling study. Environmental Pollution 62:171-182.
Ormerod, S. J., and S. J. Tyler. 1991. Exploitation of prey by a river bird, the dipper Cinclus cinclus (L.), along acidic and circumneutral streams in upland Wales. Freshwater Biology 25:105-116.
Ormerod, S. J., and S. J. Tyler. 1992. Patterns of contamination by organochlorines and mercury in the eggs of two river passerines in Britain and Ireland with reference to individual PCB congeners. Environmental Pollution 76:233-243.
Ormerod, S. J., and S. J. Tyler. 1993b. The adaptive significance of brood size and time of breeding in the dipper Cinclus cinclus (Aves: Passeriformes) as seen from post‐fledging survival. Journal of Zoology 231:371-381.
Ormerod, S. J., S. J. Tyler, and I. Jüttner. 2000. Effects of point-source PCB contamination on breeding performance and post-fledging survival in the dipper Cinclus cinclus. Environmental Pollution 110:505-513.
Ormerod, S. J., S. J. Tyler, and J. M. S. Lewis. 1985b. Is the breeding distribution of Dippers influenced by stream acidity? Bird Study 32:32-39.
Price, F. E., and C. E. Bock. 1973. Polygyny in the dipper. The Condor 75:457-459.
Robson, R. W. 1956. The breeding of the Dipper in north Westmorland. Bird Study 3:170-180.
Sæther, B. E., J. Tufto, S. Engen, K. Jerstad, O. Røstad, and J. Skåtan. 2000. Population dynamical consequences of climate change for a small temperate songbird. Science 287:854-856.
Shaw, G. 1978. The breeding biology of the Dipper. Bird Study 25:149-160.
Smiddy, P., J. O'Halloran, B. O'Mahony, and A. Taylor. 1995. The breeding biology of the Dipper Cinclus cinclus in south-west Ireland. Bird Study 42:76-81.
Sorace, A., P. Formichetti, A. Boano, P. Andreani, C. Gramegna, and L. Mancini. 2002. The presence of a river bird, the dipper, in relation to water quality and biotic indices in central Italy. Environmental Pollution 118:89-96.
Strom, S. M., H. S. Ramsdell, and A. S. Archuleta. 2002. Aminolevulinic acid dehydratase activity in American dippers (Cinclus mexicanus) from a metal‐impacted stream. Environmental Toxicology and Chemistry 21:115-120.
Sullivan, S. M. P., and K. T. Vierling. 2011. Exploring the influences of multiscale environmental factors on the American dipper Cinclus mexicanus. Ecography 34:1-13.
Taylor, A. J., and J. O'Halloran. 2001. Diet of Dippers Cinclus cinclus during an early winter spate and the possible implications for Dipper populations subjected to climate change. Bird Study 48:173-179.
Tyler, S. J., and S. J. Ormerod. 1985. Aspects of the breeding biology of Dippers Cinclus cinclus in the southern catchment of the River Wye, Wales. Bird Study 32:164-169.
Tyler, S. J., and S. J. Ormerod. 1992. A review of the likely causal pathways relating the reduced density of breeding dippers Cinclus cinclus to the acidification of upland streams. Environmental Pollution 78:49.
Tyler, S. J., S. J. Ormerod, and J. M. S. Lewis. 1990. The post-natal and breeding dispersal of Welsh Dippers Cinclus cinclus. Bird Study 37:18-22.
Vickery, J. 1991. Breeding density of Dippers Cinclus cinclus, Grey Wagtails Motacilla cinerea and Common Sandpipers Actitis hypoleucos in relation to the acidity of streams in south‐west Scotland. Ibis 133:178-185.
Vickery, J. 1992. The reproductive success of the dipper Cinclus cinclus in relation to the acidity of streams in south‐west Scotland. Freshwater Biology 28:195-205.
Walton, R. A., and K. G. Wright. 2008. Extraordinary concentration of wintering American Dippers in the Coast Range, British Columbia. British Columbia Birds 18:15-18.
Whitehorne, I. 2010. Wintering behavior, physiology and site fidelity in a partial migrant, the American Dipper (Cinclus mexicanus). Waterbirds 33:461-470.
Willson, M. F., and K. M. Hocker. 2008a. American dippers wintering near Juneau, Alaska. Northwestern Naturalist 89:24-32.
Willson, M. F., and K. M. Hocker. 2008b. Natural history of nesting American Dippers (Cinclus mexicanus) in southeastern Alaska. Northwestern Naturalist 89:97-106.
Wilson, J. D. 1996. The breeding biology and population history of the Dipper Cinclus cinclus on a Scottish river system. Bird Study 43:108-118.