News & Notes

Predicting Hummingbird Arrivals

Tuesday, April 19th, 2016
Posted on:

Spring is coming and many of our most loved birds will be here any day! Thanks to long running citizen science projects we can pretty accurately predict when certain species are going to arrive. One migrant that a lot of people are already talking about and eagerly awaiting is the Ruby-throated Hummingbird. Let’s take a look at some resources available to predict their arrival.


gorget (1)
Possibly the best known site for tracking hummingbird migrations is The owner posts little dots on a map based on reports that are submitted. The dots are labelled with a date and color based on the week. You can see the most recent updates at this link but here is a snapshot from 11 April 2016 showing where Ruby-throated Hummingbirds have been reported: (1)
Compare the map above to this map from (also a snapshot from 11 April 2016). You can also see the most recent map from eBird at this link.

eBird RTHU (1)

It is pretty clear that there are some discrepancies with these two maps, most notably that the map shows our Ruby-throated Hummingbird significantly further north than

My problem with is the lack of credibility; anyone can submit a sighting with very little review. From their site: “The map is artwork produced by hand; the dots are placed by eyeball after looking up each report in Google Maps. Reports are mapped if they illustrate migration progress, and fit without reducing legibility.” So you have reports that are going unreviewed (seriously, I think anyone could submit a report from Maine and it would be plotted because it seems to fit with the “progress”) and there is a whole issue with observer bias from the site owner plotting the location, rather than the person who actually observed the bird.

This is assuming the reported bird was even a hummingbird. Quick glimpses of kinglets hover-feeding or even large insects can easily be mistaken for hummingbirds. I do think that provides an interesting illustration of the first wave of migrants but I always struggle with the lack of credability.

On the other hand, all reports to (for Maine) that are submitted before May 1st require review from one of four state-reviewers. Here is a great article on the eBird data review process. There are currently about 15 records for Ruby-throated Hummingbirds before May 1st in Maine, for all years. From eBird, here is a frequency chart showing the timing of the Ruby-throated Hummingbird’s arrival in Maine:

frequency (1)

The first week of May
Though there are a few records in April, it is primarily in the first week of May that we should expect Ruby-throated Hummingbirds to return. So you’ve still got time to get your hummingbird feeder cleaned and hung (or your native plants sown) before these gems return.

-DougDoug Hitchcox Head Shot - please credit  M. Kathleen Kelly (1)

Meet Doug Hitchcox, Maine Audubon Staff Naturalist A Maine native, Doug grew up in Hollis and graduated from the University of Maine in 2011. Throughout college Doug worked at Scarborough Marsh Audubon Center and was hired as Maine Audubon’s staff naturalist in the summer of 2013, a long time “dream job.” In his free time, Doug volunteers as one of Maine’s eBird reviewers, is the owner and moderator of the ‘Maine-birds’ listserv and serves as York County Audubon board member and Secretary of the Maine Bird Records Committee.