This was a family holiday rather than a hard-core birding trip, but I did manage to see all target birds, so hopefully the information below will be useful to future birdwatching visitors to this beautiful archipelago. I spent four days (7-11 September) on Praslin with day trips to Cousin and La Digue and four (11-15 September) on Mahé. On Praslin you can get around very cheaply and efficiently by bus, so car rental is not necessary. Your hotel will be able to arrange a trip to Cousin; while the typical whole-day package includes Cousin, barbecue on Curieuse and snorkeling on St. Pierre, I managed to get a Cousin-only trip for €80 from Anse Volbert. On Cousin, you will be herded with two dozen mostly disinterested tourists on a standard guided itinerary. However, you should still be able to see the key birds, my guide was happy to actually have someone genuinely interested in the group. While you are supposed to stick to the group, the guide did not complain when I stayed behind. The tour boats are not allowed to land on Cousin (to prevent introduction of rats) and visitors are ferried from their boats to the beach by small boats. This can take time if there are lots of people, we had to wait almost one hour, so be prepared to wait and bring drinking water, the island was quite hot. And be prepared to end up with bird droppings on your clothing. On La Digue everything is within a walking distance, but you may also rent a bicycle. I walked from the jetty to and through the flycatcher reserve and then along the river at the east end of the reserve (partially no trail but easy during dry season) to Anse Source d'Argent. On Mahé I rented a car; the island is more mountainous and distances longer. Most species are easy to find, but the Seychelles Scops Owl and in particular the Seychelles White Eye are difficult and I only managed to find them with a guide, Perly Constance (phone +248 258 2548 ). Perly turned out to be a very knowledgeable and enthusiastic guide; he had worked on conservation projects for the Seychelles government for many years. He also helped us to find Crab Plover and Terek Sandpiper, although these would not be difficult to find on your own. The site we saw these waders (and some others) is a an artificial lagune between Victoria and the airport. Driving from Victoria on the main highway towards the airport pass the turnoff to Eden Island, cross the bridge over the outlet from the lagune, at the next roundabout make a 180 degree turn (as if you wanted to return to Victoria) and immediately veer off to the left onto a gravel road. The road is parallel to the lagune. The corner near the turnoff is the first part to emerge as the tide goes out and attracts the first birds.
There is not much point describing a detailed day-by-day itinerary; I list the species and where I saw them.
Wedge-tailed Shearwater Puffinus pacificus: many seen during ferry crossing between Mahé and Praslin, a few around Cousin.
White-tailed Tropicbird Phaethon lepturus: common on Cousin (multiple nesting on the ground right by the trail) and Mahé, you cannot miss it. Somewhat less common on Praslin or La Digue. Seeing them sailing over forest from a high point (e.g., Morne Blanc or Copolia summit) is a fantastic experience.
Frigatebirds: I saw one soaring over Cousin and one from the ferry near Praslin, both too far away to be sure about the species identity.
Grey Heron Ardea cinerea: common in channels and lagunes on Mahé.
Cattle Egret Bubulcus ibis: abundant in lagunes near Mahé airport.
Striated Heron Butorides striata: one flying along the shore on Anse Petit Coeur (Praslin), one on the small river beyond the flycatcher reserve on La Digue.
Black-crowned Night Heron Nycticorax nycticorax: one immature on the river beyond flycatcher reserve (La Digue).
Yellow Bittern Ixobrychus sinensis: one at the flycatcher reserve (La Digue), flying over the wetland (a very lucky sighting).
Seychelles Kestrel Falco araea: took some time to find them, but there was a pair on the church tower in Bel Ombre (Mahé). I found them only on my second visit to this site at 5 pm; they were not visible earlier (at 2:30 pm), presumably sheltering from sun within the tower.
Common Moorhen Gallinula chloropus: common on Cousin on the forest floor(a rather unusual habitat for Moorhen), several along the river in La Digue
Crab Plover Dromas ardeola: one at low tide at the lagune between Victoria and the airport (Mahé).
Grey Plover Pluvialis squatarola: lagune between Victoria and the airport (Mahé).
Whimbrel Numenius phaeopus: several sightings including the lagune between Victoria and the airport.
Terek Sandpiper Xenus cinerea: lagune between Victoria and the airport (Mahé).
Common Greenshank Tringa nebularia: one at the river on La Digue, one at the lagune between Victoria and the airport.
Ruddy Turnstone Arenaria interpres: one of the ferry jetty on Praslin; several at various beaches on Mahé.
Brown Noddy Anous stolidus: less abundant than Lesser Noddy, but still common on Cousin. They seem to nest preferentially in the forks between a tree trunk and a major branch, whereas Lesser Noddies prefer thinner branches away from the trunk.
Lesser Noddy Anous tenuirostris: abundant on Cousin.
White Tern Gygis alba: quite common on all islands; you get beautiful views of perching birds on Cousin.
Sooty Tern Onychoprion fuscatus: one on Cousin, several at ferry crossings.
Swift Tern Thalasseus bergii: two in Baie Ternai National Park (Mahé).
Malagasy Turtle Dove Streptopelia picturata: common everywhere. The Seychelles (sub) species does not seem to exist anymore on the main islands or Cousin.
Zebra Dove (a.k.a Barred Ground Dove) Geopelia striata: common everywhere
Seychelles Blue Pigeon Alectroenas pulcherrima: quite common on Praslin and Mahe where there are tall trees.
Seychelles Black Parrot Coracopsis barklyi: rather easy to find in Vallée de Mai, listen for the sound of food leftovers being dropped on forest floor by foraging parrots.
Seychelles Scops Owl Otus insularis: a pair at Sans-souci road near the Mission at 7 pm, with playback and Perly as the guide. The birds are attracted to playback but do not readily respond vocally, so it was only thanks to Perly's experience and keen eyesight that we were able to see them.
Seychelles Swiftlet Aerodramus elaphrus: several flying over forest at Vallée de Mai (Praslin) and Sans-souci road (Mahé).
Seychelles Bulbul Hypsipetes crassirostris: common and noisy in forested habitat. Watch them trying to extract the huge palm spiders from their webs.
Seychelles Warbler Acrocephalus sechellensis: a pair on Cousin, not easy to find. Tell the guide you are specifically interested in seeing them.
Seychelles Magpie-Robin Copsychus sechellarum: Cousin; very tame, the guides attracts them with call imitation.
Seychelles Paradise Flycatcher Terpsiphone corvina: three males and seven females; easy to find in and beyond the reserve on La Digue (look at the eye level). The staff at the little information center a the reserve will be happy to point a nest to you.
Seychelles Sunbird Cinnyris dussumieri: abundant and noisy.
Seychelles White-eye Zosterops modestus: a pair near Chemin la Misere descending to Grand Anse; it would not have been possible without Perly, so I think it is fair not to give the exact location.
Common Myna Acridotheres tristis : abundant and noisy everywhere.
Red Fody Foudia madagascariensis: abundant on Mahé and Praslin in open forests, gardens and in the streets.
Seychelles Fody Foudia sechellarum: only on Cousin, but common there, you cannot miss it.
Common Waxbill Estrilda astrild: a small flock along the river on La Digue.