On 5/22/2015, Yamashina Institute for Ornithology reported that they detected Cesium-134/137 from 92 of 92 swallow nests in Fukushima.
Overall, Cs-134/137 was measured from 150 of 182 swallow nests collected in 12 prefectures and Tokyo to include all the prefectures in Kanto, North East, North West coast and Mid Japan area except Tochigi.
The highest reading was 90,000 Bq/Kg in Fukushima. They measured Cs-134/137 even from the sample collected in Shizuoka prefecture.
This research was implemented by Yamashina Institute for Ornithology and National Institute for Environmental Studies. The samples were collected from 2011 to 2012.
It is stated in the report that the Cs-134/137 density of a nest is in proportion to the soil contamination level of the surrounding area, the reproductive performance needs to be reviewed. However, they concluded that the Cs-134/137 density of the swallow nests is not high enough to give an immediate effect to human health.
Source : Fukushima Diary