UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D. C. 20549

FORM 10-Q/A

Amendment No. 1

(Mark One)

For the quarterly period ended March 31, 2011

OR

Commission file number 1-12147

DELTIC TIMBER CORPORATION

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (870) 881-9400

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months, and (2) has been subject to such filing requirements for the past 90 days.    Yes  x    No  ¨.

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 to Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).    Yes  ¨    No  ¨.

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).   Yes  ¨    No  x.

Number of shares of Common Stock, $.01 Par Value, outstanding at March 31, 2011, was 12,565,047.

Explanatory Note

Deltic Timber Corporation is filing this Amendment No. 1 to its Quarterly Report on Form 10-Q for the period ended March 31, 2011, filed with the Securities and Exchange Commission on May 5, 2011, (“Form 10-Q”). The sole purpose of this Amendment is to furnish the interactive data files as Exhibit 101 in accordance with Rule 405 (a)(2) of Regulation S-T. Exhibit 101 to this report provides the consolidated financial statements and related notes from the Form 10-Q formatted in Extensible Business Reporting Language (“XBRL”).

No other changes have been made to the Form 10-Q. This Amendment No. 1 to the Form 10-Q speaks as of the original filing date of the Form 10-Q, does not reflect events that may have occurred subsequent to the original filing date, and does not modify or update in any way disclosures made in the original Form 10-Q.

Pursuant to Rule 406T of Regulation S-T, the interactive date files furnished as Exhibit 101 hereto are deemed not filed or part of a registration statement or prospectus for purposes of Section 11 or 12 of the Securities Act of 1933, as amended, are deemed not filed for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, and otherwise are not subject to liability under those sections.

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Item 6.    Exhibits

Index to Exhibits

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

DELTIC TIMBER CORPORATION

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