So, you’ve got your field guide, chosen your binoculars or scope and now its time to get out to the coast and get some birdwatching practice. In the fourth instalment of our Birding Basics series, Ranger Julie navigates her way through tides and explains how to predict the best time to go bird watching to maximise the number of birds you can see.
If you have spoken to experienced birders, they will recommend arriving about two to three hours before high tide in order to experience this push of birds. Alternatively, you can arrive on high tide and watch them as the tide recedes. They will then land back on the newly exposed mud so they can begin the next phase of feeding.
Get to know your patch of coast and how to read tide timetables and it will all become a lot easier, with less wasted journeys. However, it’s not all straightforward. You may have to work out when they may not arrive on time…
Tide timetables
High tide times change significantly every day, so first of all you need a timetable. This is an estimate of when high and low tide are expected and how high, or low, they will be. They are calculated well before the date in question, which you are looking for. So, whilst they indicate what might happen, they’re not a cast-iron guarantee. With this in mind, use your eyes to check if the tide really is doing what you were told it would, so that you are not stranded by the water. On our patch, for example, the footpath along the beach from Upnor to Hoo St Werburgh is covered totally covered twice a day.
The joy of watching coastal birds is that it’s not like wanting to hear the dawn chorus from forest or garden birds. For that you have to get up at the crack of dawn. We get two high and two low tides in 24 hours, so there’s always one at a time you want it. If you keep an eye on your tables.
Printed tables, how to use them
You can buy pre-printed tables in booklet form from local sailing shops, sailing clubs and boat yards. Check the booklet to see which area the tides refer to. The common default for Kent tables is Dover. You then need to search through the book for an adjustment sheet. This will list coastal areas. Identify the one closest to you. There will be a number next to it. This tells you how many hours and minutes you need to add or take away from the Dover time to get your local high tide.
Sometimes, if you buy locally produced booklets, some kind soul has adjusted the tide times for your local area. If you go online Peel Ports produce an annual set of sheets which have been calibrated for specific points on the Medway, such as Sheerness, Isle of Sheppey and Chatham. Just Google ‘Peel Ports Tide Timetables 2021’, they should be available soon.
I’ve added a link to the 2020 Chatham table so you can get some practice reading
https://www.peelports.com/media/4884/official-tide-tables-for-chatham-2020.pdf
GMT vs. BST?
The next question is. Has the table taken into consideration Greenwich Mean Time (GMT)?
Note that at the top of the sheet, on the above link, it says ‘(GMT) only’, this is common on a lot of tables. It is REALLY important. It means that the times are only accurate as written if you are looking for dates in winter… In summer we use British Summer Time (BST).
To make the sheets accurate for summer, you need to check what date the clocks change from Winter to Summertime in March and October. Then, for the summer dates within BST on the tide timetable, ADD ONE HOUR.
Too much to think about?
No problem, just do what the Bird Wise rangers do. Get an app for your phone or tablet which does all the calculations for you. The ‘Tides Near Me’ app available for both Android and IOS is one is my favourites and very accurate as it allows you to select a local tidal station to take your readings from.
How do I choose the best tide station to take a reading from?
This is where a familiarity with the local map on the app can really help.
For example, imagine I’m on the Isle of Sheppey birding…
I start off on Shellness Beach, Leysdown, Isle of Sheppey. I could take a reading from Sheerness. However, I take my reading from Whitstable Approaches. This is because they are almost opposite each other, whilst Sheerness is around the corner… The difference in tides is, on average, about 20 minutes. Not much, but can make a difference in how much bird life you see.
Then, I drive around to Elmley on Sheppey, or Oare / Conyer on the mainland. The sites are almost opposite each other overlooking the Swale, which separates the island from the mainland. I’d continue looking at the tide times for Whitstable here as, even we are on the opposite side of the island, the water flow is generally the same as Whitstable.
However, if I moved up to the Sittingbourne end of Conyer and ended up at Milton Creek I’d move to using the Grovehurst Jetty tide station instead. It’s only about 15 minutes difference from the other reading, but it is different. Knowing which tides are due first can help you plan what visit route is best to gain the best views.
It’s just a matter of thinking which tide station will be in the flow of water which is coming towards where you will be waiting for those birds.
Beware the moon, wind and pressure…
So now you know how to set a paper table right or add a tide station to your interactive map job sorted! No, sorry… We have a few wild cards to add to the mix.
1) The moon, the earth, water and gravity. Basic science here. The earth spins on its axis, this sloshes the water in the oceans. Gravity stops the water floating away from the earth. The passing moon also has gravity and pulls the sloshing water nearest it into a peak, that’s high tide. Water also peaks at high tide, on the other side of the earth, because of the spin, .
This is a great article explaining it in detail…
So what does this mean for birders?
The effect of the moon on the tides is stronger just before, at, and directly after full moon. Then we get tides which pull up higher, they also pull down lower. Tides at Chatham for example can range from 4.75 metres up to 6.06 on high tide and 0.33 to 1.3 metres on low tide. So you can see, this really alters the amount of shoreline available for birds to feed on. It can also make it very stressful for birds, as a higher tide can force them up to a metre closer to people than they would ideally like. Better to choose a birding day when there isn’t a very high pull on the tide as birds will leave the area quicker.
Full moon is generally marked on paper tables with a 0, whilst apps will sometimes give you the phase of the moon.
Tides also change when we get spring and neap tides. These again cause a weirdness in the water…
Spring tides, rather confusingly, happen all year round. They have a higher high tide than average and a lower low tide. They happen just after a full or new moon. If you ever go to Riverside Country Park and find Horrid Hill is shut because of a high tide, that’s generally why. Likewise, Raspberry Hill Lane alongside Chetney Marsh also floods at this time.
Neaps occur when the moon is in its first and third quarter after full moon. It means that that high tides are a little lower and low tides are a little higher than usual. This is a good time to bird, there is more foreshore left dry for birds to continue feeding on.
You don’t have to know all this, but it does make you look at the sea with a different eye. It almost has a personality. Want to know more? This site is great for simple explanations of weather and tide topics.
2) Wind. Wind blowing onto the land can push an advancing high tide in much faster than expected. Wind blowing off the land can hold a high tide out and make it late. Likewise, once the tide has arrived at its highest point, wind blowing onto the land can hold in a high tide and make it late dropping out. Blowing off the land, it can push a high tide out much faster. It’s better to bird on a wind blowing off the land day. The birds will hang around longer, they will also face into the wind if standing, so a better view can be had.
3) Tidal surges
We also get tidal surges. This is when a low-pressure weather system, such as a cyclone, typhoon or hurricane occurs. The drop in air pressure in the atmosphere causes the water level to rise above the normal high tide level. On top of this, the accompanying bad weather, forcing large waves in, adding even more height to the water level.
If you came on our bird walk last year at Seasalter, a tidal surge had occurred that morning. We had expected two hours of mudflats and beach to look at. Instead, we had water lapping our toes as soon as we arrived. We still had a great time and saw a black redstart, so not a disaster. However, if you are planning to travel a great distance to the coast, best to avoid a surge day, unless there are damp meadows close by where large waders, such as Curlew, will come in to grab a worm or two.
4) Estuary or bay formation
If an estuary or bay has a wide and flat entrance, the water can run in very quickly and shallowly early on. This covers the available area for birds to feed on, so smaller waders leave swiftly. Larger waders may stay longer as the depth of the water builds slowly towards the official high tide time.
If a bay, or estuary, has a sandbar across the opening, the tide may be held outside the area until it reaches a height to breach the bank. So, the tide may be late and then arrive very very quickly at a great depth. The result of this is that birds stay as long as possible and then leave swiftly.
Be wary of both effects if you are walking on the sands… They can catch you out.
Help this is all too much!
How about we all move to the Mediterranean? There, the tides only rise and fall a few centimetres… No problem!
Alternatively, the Bay of Fundy in Canada has a tidal rise and fall of up to 16metres. Our Kent tides come in around the 5-6 metre mark.
If you want to bird and get good views at any tide phase, try somewhere like the KWT nature reserve at Oare or RSPB Cliffe Pools. The birds will head out onto the Swale, or Thames, when the tide is out, then back onto the pools as it advances. If you get there a short while either side of high tide, and stand in the right place, small flocks will fly over you.
Want to know more about tides?
Try the books by local author William Thomson, who wrote The Book of Tides and The World of Tides whilst based in Deal. They will tell you everything you ever wanted to know (with lovely pictures as well)