- hybrid sparrow ID
- photographed
- sound-recorded

hybride ringmus x huismus Schiermonnikoo

Figure 1. House Sparrow x Tree Sparrow, male, Schiermonnikoog, Friesland, the Netherlands,7 May 2020 

In May 2020 we had our family spring break on the lovely Wadden Sea island of Schiermonnikoog. At our farm stay I enjoyed the many breeding House Martins, Barn Swallows, Starlings and House Sparrows – a depressingly scarce combination of birds in the Netherlands these days.


During one afternoon I caught a glimpse of a Tree Sparrow like bird, but somehow something seemed to be off. It took off so soon that I couldn’t even raise my bins. Next day I relocated it and it turned out to be a hybrid sparrow. On the third day I even got better views.


Hybrids are by definition variable. This bird certainly mostly resembled a Tree.

hybride ringmus x huismus Schiermonnikoo

Figure 2. House Sparrow x Tree Sparrow hybrid, male, Schiermonnikoog, Friesland, the Netherlands,7 May 2020

But the grey cap, a House sparrow feature, was what first triggerd me. The cap did not reach as far down in the neck as in a House. And the brown part of the cap was more richly coloured chestnut than in House, as in Tree.

hybride ringmus x huismus Schiermonnikoo

Figure 3. House Sparrow x Tree Sparrow hybrid, male, Schiermonnikoog, Friesland, the Netherlands, 7 May 2020. Note greyish, but speckled cap. It doesn't reach as far into the neck as in House. 

 The bird had subtle black markings on the chest: absent in Tree but more prominent in male House. Also check the white cheeks (as in Tree; usually greyish in House). The black cheek patches were a bit more blurred than in Tree. 

hybride ringmus x huismus Schiermonnikoo

Figure 3. House Sparrow x Tree Sparrow hybrid, male, Schiermonnikoog, Friesland,. the Netherlands, 7 May 2020. Note blackish markings on chest.

Tree Sparrow is a trifle smaller than House, but I didn't notice any size differences with the accompanying House Sparrows. I managed to make one shot with a House Saprrow in the same image:  

hybride ringmus x huismus Schiermonnikoo

Figure 5. Male House Sparrow (left) and the hybrid male, Schiermonnikoog, Friesland, the Netherlands, 7 May 2020. I didn't notice any obvious size differences.


Best of all was that I managed to make sound recordings of its song (no flight calls heard). To the human ear it sounded very much like a House. Thijs Fijen confirmed my thoughts after a quick analysis: “it mostly resembles House Sparrow”. Subtle, but significant differences are hard to pinpoint since House is very variable. So far I haven’t found any other recordings on the internet.

hybrid House x Tree SparrowVincent van der Spek
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hybride huismus x ringmus sona1.jpg

Figure 5. Spectogram of the song of the male hybrid House x Tree Sparrow onSchiermonnikoog, 6 May 2020.


Basically it behaved like a House. It appeared to be part of the local House population, feeding with the birds, singing on roofs and even aggressively chasing off a male House. 

The occurrence of House x Tree Sparrow hybrids have been described several times in the past. These often occur when either one of the species is rare (which is true for Tree on Schiermonnikoog). Harris et al. (1989), a book many of us grew up with, even depicted one. Summers-Smith (1988) mentions ten records in his sparrow monography, with eight from the UK, one from Germany and one from Poland.

Apparently Sheppard (1995) - by account of Summers-Smith - sums up over 50 records 7 years on, though I have not been able to find the original source. Two Finnish records were described by Letho (1993). Cordero & Summers-Smith (1993) even estimated hybridization to occur in Spain as often as once in every 500 pairs.

Dutch records have been described by Eigenhuis (1990) and Van den Berg & Groenendijk (1991), the latter also from Schiermonnikoog. In the open access observation database I found an additional 12 Dutch records with photographic evidence, including several from… Schiermonnikoog! The island therefore seems to be over represented in confirmed records. Overall it seems fair to say that hybridisation takes place fairly regularly, also in the Netherlands.   

hybride ringmus x huismus Schiermonnikoo

Figure 7-8. Hybrid male House x Tree Sparrow, Schiermonnikoog, Freisland, the Netherlands, 7 (upper) and 6 May 2020. Note 'smudged' cheek patch.

hybride ringmus x huismus Schiermonnikoo

A final word: James Denis Summers-Smith
The expert on sparrows was British ornithologist J. Denis Summers-Smith. He wrote the family monograph, as well as the the single species monographs on both House and Tree Sparrow, and he was the author on the sparrow section of Handbook to the Birds of the World (HBW). He published about hybrids several times, more than anyone else. Remarkably Summers-Smith, aged 99, passed away on 5 May 2020 - the very same day I first saw the above described hybrid! Isn't that a poetic coincidence? This online note is in memory of this devoted sparrow researcher and top notch amateur scientist. 

Thijs Fijen kindly analysed my sound-recording. 



Berg, G. van den & Groenendijk, D., 1991. Hybride Huismus x Ringmus op Schiermonnikoog in mei 1989. Dutch Birding 13: 66-67.


Cordero, P.J., Summers-Smith, J.D., 1993. Hybridization between House and Tree Sparrow (Passer domesticus, P. montanus). J Ornithol 134: 69–77

Eigenhuis, K. J. 1990. Hybride Huismus x Ringmus te Aalsmeer in januari-februari 1990. Dutch Birding 12: 186-187.


Harris, A., Tucker, L. & Vinicombe, K., 1989. Thre Macmillan field guide to bird identification. London.


Letho, H., 1993. House Sparrow x Tree Sparrow hybrids in Finland. Birding 15: 264-265.

Sheppard, R. 1995: Hybrid Tree x House Sparrow in County Donegal. Irish Birds 5 (3): 319-320.

Summers-Smith, J.D., 1988. The sparrows. A study of the genus Passer. Poyser, London.