After two months in Texas, I finally had the long-awaited opportunity to head south – seriously south. The lower Rio Grande valley along the border with Mexico is a unique bird area, as it holds a wide range of tropical species at the far northern end of their range which are not found elsewhere in the USA. It’s arguably one of the most exciting places in the world to see birds – especially so in spring, but winter is certainly not without its delights, as I was to discover.

Along the way, what self-respecting birder could pass up the opportunity to visit Aransas National Wildlife Reserve – the only wintering site in the world for the rare and spectacular Whooping Crane? I was at the Aransas visitor center by 7.30am after a ridiculously early start from Houston. The weather wasn’t especially co-operative, being very windy and overcast with occasional outbreaks of rain. Considering this is December in the northern hemisphere, one might imagine some very unpleasant birding conditions, but not today in southern Texas where the temperature stayed pegged at an extremely mild 25C (78F) throughout the day.

Five gleaming white Whooping Cranes were easy to spot from the specially constructed viewing tower, albeit very distantly (a telescope is essential here). I also had to clear a path through the rows of Black Vultures, who like to use the railings on the tower’s walkways as perching and squabbling grounds, and in some cases were very reluctant to move – these birds are actually fairly intimidating when they are glaring at you from only six feet away!

I enjoyed some seawatching in the bay, although in less than ideal conditions with the wind and choppy seas making for difficult viewing. However, I did find about 10 Horned Grebes, perhaps a higher than usual total for this site, and at least four Greater Scaup among the large flocks of Lesser Scaup. Interesting fly-bys comprised a small flock of Snow Geese, and three cinnamon-colored Long-billed Curlews, but try as I might, I could not locate a Common Loon on the water.

Along the “auto tour loop”, I chanced upon a family group of Sandhill Cranes showing well not far from the car, and a lone Whooping Crane nearby, closer than the tower birds but standing in long grass so it was only visible from the neck upwards. White-tailed Hawk was another good sighting here, this bird is a speciality of the Texas coastal plain and is found nowhere else in the USA.

Although the Aransas area easily merits a full day – or even several days – of exploring, I had lots more birds to see and only limited time, so by late morning I was impatient to hit the road south. An eBird-inspired stop south of Corpus Christi was moderately rewarding, with good views of several Greater Roadrunner, a fine male Pyrrhuloxia, and three Say’s Phoebes at Chapman Ranch. I had been hoping for Burrowing Owl here, but the Say’s Phoebes provided excellent compensation – they are rare winter visitors this far east. I managed a very poor photo with my “punk” camera, but it’s enough to confirm the identification. I really need to invest in a decent camera, as photos are more or less essential these days in order to confirm sightings of rare species – and I was to find several other rarities before the weekend was out, neither of which I managed to photograph.

Vast agricultural prairies lie to the south and west of Corpus Christi, home in winter to very small numbers of Sprague’s Pipit, Mountain Plover, and Prairie Falcon, but finding any of them is locating a needle in a haystack, and on this windy and dull afternoon it was unsurprising when I came away empty-handed – although a fine flock of Sandhill Cranes provided modest compensation for my efforts.

With an early, wintry dusk fast approaching, the birding was more or less over for the day, and I drove south to Harlingen, where I treated myself to an overnight stay in a Super 8 motel. This was a bit above budget – I had been planning to sleep in the car – but I was exhausted after the early start and long drive.

I awoke to more of the same weather – extremely overcast, warm, windy, and damp. With so many birding options in the lower Rio Grande valley, it was hard to decide where to go – and with just one full day here, I had to be smart and eliminate any long drives. The original plan to visit Laguna Atascosa fell by the wayside in favor of the much closer Estero Llano Grande State Park, which turned out to be an excellent choice. A total of 76 bird species seen here in just 3.5 hours demonstrates the quality of this location. In fact, just sitting quietly and watching the bird feeders and garden at the visitor center produced such exciting birds as Buff-bellied Hummingbird, Green Jay, Altamira Oriole, and both Curve-billed and Long-billed Thrashers, all at very close range. Along the trails, I was adding to my list every few minutes, with many south Texas specialities seen including Cinnamon Teal, Plain Chachalaca, White-tipped Dove, Common Ground-Dove, Green Kingfisher, Groove-billed Ani, Green Parakeet, Great Kiskadee, Tropical Kingbird, Indigo Bunting, a beautiful male Painted Bunting (a very rare bird in winter), and a perfectly camouflaged day-roosting Common Pauraque.

Halfway through the morning, the wind suddenly blew cold, and I was to learn later that the temperature dropped from 25C (78F) to 16C (61F) in just a couple of seconds. Sudden weather changes are a fascinating Texas phenomenon that we just don’t have in temperate Western Europe. All I know is that suddenly I was very grateful I had packed my warm sweater in my bag – other T-shirt wearing birders I encountered on the trails weren’t so lucky!

My second port of call for the day was the Santa Ana National Wildlife Reserve, where a long-staying Northern Jacana, a very rare vagrant to the USA from its breeding grounds in Mexico, was perhaps the outstanding highlight. The area didn’t seem quite as exceptionally rich in birds as Estero Llano Grande, but I added some excellent birds to the list including a skulking Olive Sparrow, a Harris’s Hawk, and one of my all-time favorite birds, Black-and-white Warbler. This charismatic bird is readily spotted by its striped black and white plumage, and its unusual habit of spiralling up and down trunks and branches, more like a nuthatch than a warbler. It’s common in the USA in from spring to fall, but only a handful winter in the far south of the country, with the rest heading to Mexico and central America. Not that this one was very far from Mexico, perhaps just two miles as the warbler flies.

I was to have an even closer encounter with Mexico at my final location for the day, the Bentsen-Rio Grande State Park. This site, also known as the World Birding Center, is legendary among birders, with quite a long list of very rare Mexican and tropical species seen here over the years. I arrived in the early afternoon to glorious sunny, cool and calm conditions, the incoming cold front having taken just a couple of hours to completely clear the overcast, windy weather away.

Birding the Bentsen-Rio Grande State Park involves doing quite a lot of walking, as it’s a big park and cars are not allowed, presumably in a bid to make it harder for illegal immigrants to cross the USA-Mexico border which lies along the Rio Grande at the southern edge of the park. Despite the fine weather, birding was rather slow at first, although I wasn’t complaining as the numerous Green Jays at the park’s feeding stations were always on view and looking spectacular in the afternoon sunlight.

The main reason I was here was for the hawks, and I after nearly four hours in the park, and more than six miles of walking, I came away well satisfied with excellent views of two perched adult Grey Hawks (a site speciality), Harris’s Hawk, White-tailed Hawk, Cooper’s Hawk, and good perched views of the long-staying juvenile Broad-winged Hawk. The latter species is a common summer visitor and passage migrant to the USA, but very rare in winter.

The habitat is rather dry and arid in the park, and bird density seemed fairly low. I figured that maybe if I headed to the distant reaches of the park next to the Rio Grande, there might be some damper areas with perhaps a wider range of bird species. This didn’t actually prove to be the case, but I had an interesting experience when I followed a small side trail and suddenly found myself on the banks of the Rio Grande. Across the river, perhaps 200 feet away, was Mexico, and on the opposite bank I could see a derelict building and beside it, a narrow path heading to the water’s edge. On my side of the river, a deflated inner tube lay in the shallows, no doubt previously used by illegal immigrants heading across from Mexico. It really would not have been hard to cross the river undetected in this spot, and disappear into the woods in the State Park – I wondered how many people used this particular crossing, and whether anyone was lurking in the bushes watching me at that moment!

As the afternoon drew to a close, I dosed up on some coffee, and drove north through the evening, finally arriving at the gates of Aransas NWR at around 11.30pm. I was well-prepared with blankets and pillows, and enjoyed a surprisingly refreshing sleep in the car, waking at 7.00am ready and raring to go for another morning’s birding.

It was one of those mornings when the world seems absolutely perfect. A clear, sunny, and cool day, with temperatures of 7C/45F at dawn rising to perhaps 17C/63F by late morning. A little mist lingered over the trees and I could hear the distant calls of Sandhill Cranes in flight, and one of the first sights to greet me at the start of the Heron Flats trail was a magnificent pair of Whooping Cranes on the saltmarsh close to the first viewing platform.

The Heron Flats trail was absolutely bursting with bird activity, with small songbirds and wintering warblers energetically feeding as the sun warmed the trees and bushes, making up for lost time after the recent windy, rainy weather. Yellow-rumped Warblers inhabited virtually every bush, calling constantly, and some usually secretive species showed well: two Sedge Wrens, three Grey Catbirds, and no fewer than five Long-billed Thrashers.

It was on this trail that I found a major winter rarity. Noticing a warbler quite low down in brushy scrub at the edge of the path, I raised my binoculars and immediately knew I was onto something good. It had a bright, vivid yellow throat and underparts, black streaking on the breast sides, a plain olive-green back with no discernible wingbars, and clear yellow crescents above and below the eye. The bird was feeding low down in the bushes, flicking its wings and tail, and showing very well in perfect light as I had the sun behind me. The all-yellow underparts and lack of wingbars ruled out Pine Warbler, the only realistically confusable possibility among the regular wintering warblers. I realized I could only have been looking at a Prairie Warbler, which is an exceptionally rare bird in Texas, especially in winter. A few days later, when perusing records of this species on eBird, I found that a juvenile female Prairie Warbler had been seen (and photographed) at exactly the same location in December last year. Could my bird be the same individual, returning for a second winter?

Full bird list, south Texas, December 12th-14th. Lifers in bold, 2015 year ticks in italics:

1. Black-bellied Whistling Duck
2. Snow Goose
3. Gadwall
4. American Wigeon
5. Mottled Duck
6. Blue-winged Teal
7. Cinnamon Teal
8. Northern Shoveler
9. Northern Pintail
10. Green-winged Teal
11. Redhead
12. Greater Scaup
13. Lesser Scaup
14. Bufflehead
15. Common Goldeneye
16. Red-breasted Merganser
17. Plain Chachalaca
18. Least Grebe
19. Pied-billed Grebe
20. Horned Grebe
21. Eared Grebe
22. Neotropic Cormorant
23. Double-crested Cormorant
24. Anhinga
25. Brown Pelican
26. American White Pelican
27. Great Blue Heron
28. Great Egret
29. Snowy Egret
30. Little Blue Heron
31. Tricolored Heron
32. Reddish Egret
33. Yellow-crowned Night Heron
34. Black-crowned Night Heron
35. White Ibis
36. White-faced Ibis
37. Roseate Spoonbill
38. Black Vulture
39. Turkey Vulture
40. Osprey
41. White-tailed Kite
42. Northern Harrier
43. Sharp-shinned Hawk
44. Cooper’s Hawk
45. Harris’s Hawk
46. White-tailed Hawk
47. Grey Hawk
48. Broad-winged Hawk
49. Red-tailed Hawk
50. Sora
51. Common Gallinule
52. American Coot
53. Sandhill Crane
54. Whooping Crane
55. Black-necked Stilt
56. American Avocet
57. Killdeer
58. Northern Jacana
59. Spotted Sandpiper
60. Greater Yellowlegs
61. Willet
62. Long-billed Curlew
63. Ruddy Turnstone
64. Sanderling
65. Western Sandpiper
66. Least Sandpiper
67. Long-billed Dowitcher
68. Wilson’s Snipe
69. Laughing Gull
70. Ring-billed Gull
71. Caspian Tern
72. Forster’s Tern
73. Rock Dove
74. Eurasian Collared Dove
75. Inca Dove
76. Common Ground-Dove
77. White-tipped Dove
78. White-winged Dove
79. Mourning Dove
80. Greater Roadrunner
81. Groove-billed Ani
82. Common Pauraque
83. Ruby-throated Hummingbird
84. Buff-bellied Hummingbird
85. Green Kingfisher
86. Belted Kingfisher
87. Golden-fronted Woodpecker
88. Ladder-backed Woodpecker
89. Crested Caracara
90. American Kestrel
91. Green Parakeet
92. Eastern Phoebe
93. Say’s Phoebe
94. Vermilion Flycatcher
95. Great Kiskadee
96. Couch’s Kingbird
97. Tropical Kingbird
98. Loggerhead Shrike
99. Green Jay
100. Tree Swallow
101. Cave Swallow
102. Black-crested Titmouse
103. House Wren
104. Sedge Wren
105. Carolina Wren
106. Blue-grey Gnatcatcher
107. Ruby-crowned Kinglet
108. American Robin
109. Grey Catbird
110. Curve-billed Thrasher
111. Long-billed Thrasher
112. Northern Mockingbird
113. European Starling
114. Black-and-white Warbler
115. Orange-crowned Warbler
116. Common Yellowthroat
117. Yellow-rumped Warbler
118. Prairie Warbler
119. Olive Sparrow
120. Savannah Sparrow
121. Lincoln’s Sparrow
122. Swamp Sparrow
123. Northern Cardinal
124. Pyrrhuloxia
125. Indigo Bunting
126. Painted Bunting
127. Red-winged Blackbird
128. Eastern Meadowlark
129. Boat-tailed Grackle
130. Great-tailed Grackle
131. Altamira Oriole
132. American Goldfinch
133. House Sparrow

World Life List: 2,054
2015 World Year List: 1,108