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