Help please...Weather conditions / migrant falls...south-east England (1 Viewer)

Could anyone please clarify for someone becoming increasingly confused when trying to find out more information on this:

What are the absolute 'ideal' conditions to look for when planning a trip to a spring migration hot-spot? We'll be in mid-May soon, and the prevailing wind speed and strength seem to have seriously reduced migrant falls during the last three weeks at the traditional south-east sites (Dungeness, Portland, Beachy Head, etc). I mean land-birds, not sea-watching.

Perhaps I should re-phrase the question to ask: What conditions would make a day-trip to a south-east coastal site a no-go? I'm assuming that the predicted weather for Thursday at Dunge - light rain and 35mph south-westerlies fall into this category?!

Thanks

Hi LYM

I'm giving this a bump. I think it's a good question and I too hope you'll get some answers.

I went to Whitbred Hollow last week for the first time. Have you ever been there? I believe it's very good, less than a mile from Beachy Head. I thought I heard a grasshopper warbler. It was quite blustery, SW winds, but a steady stream of swallows arriving off the sea and a few whitethroats.

Joanne

Portland had a huge fall on 4 May - see their website for details!

Interestingly, this was not reflected at my local patch, just 30-odd miles to the east. This is often the case, and it would be great to know the reasons. I can only assume that "ideal" conditions are to some degree site-specific.

To generalise - the best falls usually occur when there has been a period of "blocking" weather such as heavy rain or strong opposing winds, the longer the period the better, with falls occurring once the weather changes. A break in settled weather can have a similar effect, with "surprised" migrants hitting a weather system and being grounded as a result. However, you have to consider the conditions en-route, so what appears to be ideal conditions on a local basis may prove to be unproductive due to the situation across the channel.

I am also a believer in "long vectors" - if you look at the pressure charts and imagine the isobars as pathways, see where the paths start and end, work out the wind direction, and see if there's a corridor with tailwinds from an interesting area (eg from the Med at this time of year, helping overshooting migrants, or from much further afield in the autumn). The longer such a corridor is in place, the more likely it is to assist the migrants. If you then see a weather front drifting down across the UK from the north, if it hits the south coast overnight or around dawn, it is likely to produce a fall!

Regarding your question re. Dunge, I'd be most surprised if there were many land migrants about, as the weather has been pretty poor for a few days, but the sea might be worth a look. If the poor weather is reflected on the near continent, look for breaks in the weather. At this time of year the pressure to migrate is very strong as time is already running out for establishing territory, finding a mate and breeding, so you'll get some movement whenever conditions allow.

Thanks for the responses...most helpful.

Joanne...I have been to Beachy Head several times this spring, but have not encountered any significant migrant arrivals (yet). I shall keep watching the weather for those south-easterlies...

Try looking for light head wind conditions. You only have to look at todays and yesterdays falls to see what I mean. Heavy overnight cloud has forced many birds to move during the day in the last 2 days. A fall of 100+ Sedge warblers is not surprising as you can see from todays surface pressure chart there has been a head wind all around the welsh coast. Yesterday a head wind along the north-east coast saw a fall of common migrants at spurn of 300 wheatear, 150 willow warbler, 32 whinchat, 12 ring ouzels, 21 spot fly.
Why do they like head winds. that's easy to explain. wind flowing over a birds wings give them lift. the wing is curved from front to back making air flow quicker over the top than the bottom. if a bird doesn't have to fly forward to make this airflow happen because of a head wind then this becomes an energy saver.
regards,
Paul Bowyer
http://www.birdlist.co.uk

pabs said:

Why do they like head winds. that's easy to explain. wind flowing over a birds wings give them lift. the wing is curved from front to back making air flow quicker over the top than the bottom. if a bird doesn't have to fly forward to make this airflow happen because of a head wind then this becomes an energy saver.
regards,
Paul Bowyer
http://www.birdlist.co.uk

Click to expand...

Hello Paul,
I think i've read your theories about this on your website, and it makes a lot of sense.. I always wondered why birds like Swallows were always seemingly battling against the wind on migration!
One thing I can never work out is how birds get blown off course, if they prefer to fly into the wind.. is it fine when they depart, but then they get caught in the strong winds, and just have to go with the flow? literally!

I live about 15 miles inland from the south coast, and the local birding was dire for a couple of weeks in April this year.. Clear skies and southerly winds must have equated to birds just passing straight over.. the minute we had some rain: Double figure Wheatears and a Whinchat appeared in a flash.
I've also given up going out seeking migrants when the wind is strong and from the west!

Excellent topic, I guess we all wish we knew the answers!
Peter

pabs said:

Try looking for light head wind conditions.
Why do they like head winds. that's easy to explain. wind flowing over a birds wings give them lift. the wing is curved from front to back making air flow quicker over the top than the bottom. if a bird doesn't have to fly forward to make this airflow happen because of a head wind then this becomes an energy saver.
regards,
Paul Bowyer
http://www.birdlist.co.uk

Click to expand...

Thanks Paul, makes good sense with the emphasis on the light headwinds. I'll keep this in mind.

gyrfalcon said:

Hello Paul,

I live about 15 miles inland from the south coast, and the local birding was dire for a couple of weeks in April this year.. Clear skies and southerly winds must have equated to birds just passing straight over.. the minute we had some rain: Double figure Wheatears and a Whinchat appeared in a flash.
I've also given up going out seeking migrants when the wind is strong and from the west!

Excellent topic, I guess we all wish we knew the answers!
Peter

Click to expand...

True about the wheatears this year, Peter. I was at Newhaven Tide Mills on just the right day, well into double figures.

Joanne

Coincidentally, I'm still bumping into wheatears (7 and 1 yesterday) on the Hampshire Downs, but as this is my first Spring since moving into this area, I'm still finding the good sites, and haven't a clue how long these have been in the area, or what weather brought them down.

Hi Peter,
yes I agree that birds do get caught out sometimes with a weather front which causes them to get blown off course. This often happens in the severn estuary with a strong westerly. It's not just sea birds but waders, terns, raptors etc. I agree also with what you say about the clear blue skies and light winds (high pressure weather) with the birds going straight over. The slightest hint of bad weather and there they all are. One additional point, I found that evening watches can be productive on days with high pressure.

Regards,
Paul