As of yesterday, the updated forecast for budburst on the mid-elevation bird plot (490 m asl) is … TODAY!

In a few weeks, we will be able to compare our sequence of forecasts for 2021 with the official outcome as measured by Amey Bailey. Over 28 years, the predicted date of leaf-out based on degree days > 4 C accumulated after 22 March has tended to be within about 2 days of the observed date (mean ± SD of observed – predicted = -0.4 ± 2.0 days). If this year’s prediction holds, leaf-out in 2021 will be within the historical distribution but on early side: about 7 d earlier than the average since 1956 and about 5 days earlier than that predicted for 2021 based on the 60-year trend for earlier springs.

The sequence of forecasts for this year have been reasonably steady. Today’s prediction of leaf-out on 8 May is three days later than the prediction of 5 May from the first forecast of the year one month ago.

For those of you interested in the life of autotrophic denizens of the understory such as hobblebush, spring ephemerals, and stream algae, this could be a pretty good year. The forecast date for canopy closure (90% leaf expansion) at mid-elevation is 23 May. This 15-day window of phenological opportunity in the understory would be a bit longer than average (range = 8 to 22 days).

The current forecast date for median arrival of Black-throated Blue Warblers is next Wednesday. The forecast date for initiation of their first clutch is 30 May.

Further details in enclosure. Feel free to share this with anyone.

Matt