The 850 mb chart is useful to monitor air mass advection and forecasting night time low and daytime high temperatures.  So it turns out that the 850mb chart is also useful for tracking migratory birds.

The Cruising altitude of many migratory birds can be as high at 6000 ft.  Monitoring the wind fields of the 925mb and 850 mb charts can be helpful in being at the right place and at the right time for spotting the arrival of the migratory bird of your choice.

The altitude of 925 mb is approximately 2498 feet and the altitude of 850mb is 4781 feet. For those bird species that fly at higher altitudes, you can even indulge in the 700mb chart at around 9882 feet.

The 925 and the 850 mb charts  can be used more or less interchangeably for monitoring migratory birds because the difference in height isn’t that significant for those purposes.  Often an 850 mb chart is often easier to obtain than a 925mb chart.

How to use this charts. Look at the wind barbs.  Wind barbs have valuable information regarding wind speed and direction. To read a wind barb, look at the long shaft which indicates the direction the wind is coming from, and the barbs on the shaft represent wind speed: one long barb equals 10 knots, while a short barb equals 5 knots. For speeds over 50 knots, a pennant is used along with the barbs.

The image above from UCAR is a great pictorial to get you started. Once you get the idea, reading wind fields on pressure maps isn’t so bad.  Now interpreting the wind information on a 925mb or and 850 mb is pretty straightforward.  Try reading the information portrayed on the 850 mb map at the top of the page.  What is the wind direction and speed?